Developmentally regulated cell surface expression and function of c-kit receptor during lymphocyte ontogeny in the embryo and adult mice

We have used a c-kit-specific monoclonal antibody, immuno-fluorescence staining and flow fluorocytometry or microscopy analysis to assess the cell surface expression of the c-kit receptor on a panel of non-transformed clones representing different stages of T- and B-lymphocyte development, freshly isolated lymphoid cells from thymus, bone marrow and spleen of young adult C57BL/6 mice and cells from yolk sac, thymus and liver of developing C57BL/6 mouse embryos. Pro-T, Pro-B and Pre-B clones derived from thymus or liver of 14-day embryos are c-kit+. Starting at day 8 to 8.5 in yolk sac, day-10 in fetal liver, and day 11 to 12 in fetal thymus, there are many c-kit+ cells. The number of c-kit+ cells in liver and thymus increases up to day 15 and progressively decreases thereafter. Cell sorter purified c-kit+ day 14 fetal liver cells fully reconstitute the T and B cell compartments of immunodeficient Scid mice. Stromal cells or epithelial cells derived from fetal thymus or liver, which can support growth and differentiation of c-kit+ lymphocyte progenitor clones, synthesize mRNA for Steel Factor (SF), the ligand of c-kit. In the adult mouse, however, c-kit expression is restricted to very early stages of T- and B-lymphocyte development (multipotent progenitors, B-cell/myelocytic progenitors, Pro-T and Pro-B lymphocyte progenitors). Most cells at the Pre-T, Pre-B and later stages of development do not bear detectable c-kit. Using Cos-1 cells transfected with mouse SF-cDNA and an antagonistic c-kit receptor-specific antibody, we show that the c-kit/SF system contributes to the survival of lymphocyte progenitors and enhances the proliferative responses of these cells to other growth factors (i.e. IL2, IL3, IL4, IL7). However, the c-kit receptor/SF ligand pair is neither sufficient nor necessary for the differentiation of lymphocyte progenitors into mature T- or B-lymphocytes. Finally, in stromal cell lines from fetal liver and adult bone marrow and thymic epithelial cell lines the level of steady state SF-RNA transcripts is inversely correlated with that of IL-7-mRNA. Moreover, IL7 inhibits the synthesis of SF-mRNA in stromal cells and rIL6 abrogates this inhibitory effect of rIL7. Thus, the expression of SF in stromal cells is subjected to complex regulation by other cytokines produced by the same stromal cells or by neighboring cells in a given microenvironment.(ABSTRACT TRUNCATED AT 400 WORDS)

T cell receptor (TCR) beta chain homodimers on the surface of immature but not mature alpha, gamma, delta chain deficient T cell lines

Transfected T cell receptor (TCR) beta chain genes are expressed as homodimers on the surface of immature (Sci/ET27F) but not on mature (58 alpha-beta-) T cell lines which lack TCR alpha, gamma and delta chains. The homodimer on Sci/ET27F cells is tightly bound to CD3 delta and CD3 epsilon while the association with CD3 gamma and CD3 zeta proteins is rather weak. Crosslinking of the TCR beta homodimers resulted in a strong and rapid calcium flux. In 58 alpha-beta- T cells the beta TCR chain could be easily visualized intracellularly but was not transported to the cell surface. The Scid cell lines considerably facilitate the molecular analysis of early differentiation events in the thymus which are likely to be regulated by the beta TCR homodimer.

Thymic hyperplasia in transgenic mice caused by immortal epithelial cells expressing c-kit ligand

To dissect mechanisms that co-ordinate specific events in thymopoiesis we have characterized alterations in thymic structure and function caused by expression of a transgene. This gene encodes SV40Tag and is specifically expressed in a subset of thymic epithelial (TE) cells around birth. As a result the number of immortal TE cells increases, thymic mass increases (up to 3 g), and thymopoiesis is expanded. The latter is reflected by a approximately 100-fold increase of the major thymocyte subsets and increased peripheral T cell counts. Grossly hyperplastic thymi retain many but not all morphological features of a normal thymus. Also in grafts, SV40Tag+ TE cells steer expansion (up to 8 g) and organize a tissue with mainly cortex-like features that includes mainly SV40Tag+ TE cells, thymocytes, and macrophages. To investigate expression of specialized gene functions in the immortal TE cells, a cell line was derived. The Epi-A1 cell line expresses the genes for major histocompatibility complex class I and II, Thy-1, interleukin (IL)-6, IL-7, macrophage-colony-stimulating factor, and transforming growth factor-beta 3. Most importantly, Epi-A1 cells also express the IL-4 receptor and the c-kit ligand (KL), a factor that, in concert with commitment factors, channels progenitors into hemopoietic lineages. The expression of low constitutive levels of KL mRNA does not require IL-4, but KL mRNA levels are increased dramatically in response to IL-4. Since constitutive expression of KL mRNA in vivo is restricted to a small subset of TE cells in the thymus, our findings reveal a novel specific interaction between thymocytes and a specialized subset of TE cells.

Comparison of in-house reference extracts of Dermatophagoides pteronyssinus and Phleum pratense with the WHO International Standards

Two of the WHO First International Standards (IS) of allergenic extracts, the corresponding to Dermatophagoides pteronyssinus (House dust mite) and phleum pratense (Thymothy grass), have been used to assess the quality of our in-house reference preparations (IHR) and to calibrate their relative potency. The qualitative comparison was achieved by SDS-PAGE, Agarose-IEF and their respective enzime immunoblottings (Western blot and immunoprinting). The band patterns obtained were fairly similar for both Phleum pratense extracts. With the exception of two basic IgE binding proteins not detected in the IEF-blotting of the International Standard. However, several differences were noted between IS and IHR Dermatophagoides pteronyssinus extracts, indicating so the higher raw material heterogeneity. The difference was specially remarkable at the level of SDS-PAGE Immunoblotting since while our IHR extract showed similar ratio of Der p I to Der p II major allergens, the IS exhibited a large preponderance of Der p I, with Der p II allergen scarcely detected by our chromogenic method. Calibration of potency was done by means of RAST inhibition, therefore allowing the expression of our extract concentrations in International Units. The higher degree of homogeneity between Phleum pratense extracts was corroborated by the comparison of slopes from the RAST-inhibition plots.

Mercurialis annua pollen: a new source of allergic sensitization and respiratory disease

Sensitization to Mercurialis annua pollen in 13 patients admitted for allergy study of asthma, rhinitis, or rhinoconjunctivitis is described. Twelve of these patients were also sensitized to other common aeroallergens. In five patients, a relationship was found between exposure to M. annua pollen and elicitation of symptoms. All patients were prick test and RAST positive to an extract of M. annua pollen. Nasal provocation test proved positive in 10 of 12 patients, and bronchial provocation test was positive in the only patient in whom it was performed. Two late responses were recorded. Immunoblotting of the 13 sera revealed two different groups of relevant allergens; one of isoelectric point 10.2, reacting with 12 of the 13 sera, and the other allergen of isoelectric point 5.0 to 5.5, reacting with 11 of the 13 sera. M. annua pollen is able to induce both sensitization and clinical disease in atopic patients. Since sensitization to this pollen accounts for 8.5% of total positive skin tested patients in the same period, we believe M. annua pollen should be considered as a relevant allergen and thus included in skin test batteries. Some patients labeled as having "intrinsic" asthma or rhinitis might be sensitized to this and other previously unknown allergens.

Fetal liver pro-B and pre-B lymphocyte clones: expression of lymphoid-specific genes, surface markers, growth requirements, colonization of the bone marrow, and generation of B lymphocytes in vivo and in vitro

We describe here the development and characterization of the FLS4.1 stromal line derived from 15-day fetal liver of BALB/c embryos and defined culture conditions that efficiently support the cloning and long-term growth of nontransformed B-220+ 14-day fetal liver cells at two stages of B-cell development, namely, pro-B lymphocytes (immunoglobulin [Ig] genes in germ line configuration) and pre-B cells (JH-rearranged genes with both light-chain Ig genes in the germ line state). All B-cell precursor clones require recombinant interleukin-7 (rIL-7) and FLS4.1 stromal cells for continuous growth in culture, but pro-B lymphocyte clones can also proliferate in rIL-3. None proliferate in rIL-1, rIL-2, rIL-4, rIL-5, rIL-6, or leukemia inhibitory factor. FLS4.1 stromal cells synthesize mRNA for Steel factor but not for IL-1 to IL-7; all pro-B and pre-B clones express c-Kit, the receptor for Steel factor, and a c-Kit-specific antibody inhibits the enhanced proliferative response of fetal liver B-220+ B-cell precursors supported by FLS4.1 stromal cells and exogenous rIL-7 but does not affect that promoted by rIL-7 alone. Northern (RNA) blot analysis of the expression of the MB-1, lambda 5, Vpre-B, c mu, RAG-1, and RAG-2 genes in pro-B and pre-B clones show that transcription of the MB-1 gene precedes IgH gene rearrangement and RNA synthesis from c mu, RAG-1, RAG-2, lambda 5, and Vpre-B genes. All clones at the pre-B-cell stage synthesize mRNA for c mu, RAG-1, and RAG-2 genes; transcription of the lambda 5 and Vpre-B genes seems to start after D-to-JH rearrangement in B-cell precursors, indicating that the proteins encoded by either gene are not required for B-cell progenitors to undergo D-to-JH gene rearrangement. These findings mark transcription of the MB-1 gene as one of the earliest molecular events in commitment to develop along the B-lymphocyte pathway. Indeed, both pro-B and pre-B clones can generate in vitro and in vivo B lymphocytes but not T lymphocytes; moreover, these clones do not express the CD3-gamma T-cell-specific gene, nor do they have rearranged gamma, delta, or beta T-cell antigen receptor genes.

EA-1, a novel adhesion molecule involved in the homing of progenitor T lymphocytes to the thymus

The mouse progenitor T lymphocyte (pro-T) cell line FTF1 binds in vitro to thymus blood vessels, the thymic capsule, and liver from newborn mice. A mAb, EA-1, raised against an embryonic mouse endothelial cell line, blocked adhesion. The antibody also interfered with pro-T cell adhesion to a thymus-derived mouse endothelial cell line; it had no effect on the adhesion of mature T lymphocytes and myeloid cells. The antigen recognized by EA-1 is located on the vascular endothelium of various mouse tissues and absent on pro-T cells. EA-1 antibody precipitates molecules with apparent molecular weights of 110,000, 140,000, 160,000, and 200,000. Immunoclearing and binding-inhibition studies with antibodies against known adhesion molecules suggest that the EA-1 antigen is a novel adhesion molecule involved in colonization of the embryonic thymus by T cell progenitors.

Structural complexity of the symbiotic plasmid of Rhizobium leguminosarum bv. phaseoli

The complete physical map of the symbiotic plasmid of Rhizobium leguminosarum bv. phaseoli strain CFN42 was established. The data support the concept that Rhizobium symbiotic genes are part of a complex genomic structure which contains a large amount of reiterated DNA sequences. This plasmid is a circular structure of 390 kb with approximately 10 families of internally reiterated DNA sequences of two to three elements each. One family includes two directly oriented nitrogenase operons situated 120 kb apart. We also found several stretches of pSym that are reiterated in other replicons of the cell. Localization of symbiotic gene sequences by heterologous hybridization revealed that nodABC sequences are separated in two regions, each of which contains a nod boxlike element, and it also suggested the presence of two copies of the nifA and nodD gene sequences. We propose that the complex structure of the symbiotic plasmid allows interactions between repeated DNA sequences which, in turn, might result in frequent rearrangements.

Amplification and deletion of a nod-nif region in the symbiotic plasmid of Rhizobium phaseoli

One remarkable characteristic of the genomes of some Rhizobium species is the frequent occurrence of rearrangements. In some instances these rearrangements alter the symbiotic properties of the strains. However, no detailed molecular mechanisms have been proposed for the generation of these rearrangements. To understand the mechanisms involved in the formation of rearrangements in the genome of Rhizobium phaseoli, we have designed a system which allows the positive selection for amplification and deletion events. We have applied this system to investigate the stability of the symbiotic plasmid of R. phaseoli. High-frequency amplification events were detected which increase the copy number of a 120-kb region carrying nodulation and nitrogen fixation genes two to eight times. Deletion events that affect the same region were also found, albeit at a lower frequency. Both kinds of rearrangements are generated by recombination between reiterated nitrogenase (nifHDK) operons flanking the 120-kb region.

Development of lymphocytes in interleukin 7-transgenic mice

We have developed and established mouse transgenic lines in which the mouse interleukin 7 gene was targeted for expression in the lymphoid cell compartment. Northern blot analysis indicate that the transgene is expressed in bone marrow (BM), spleen and thymus, but not in kidney, liver, brain or heart. Both the frequency and absolute numbers of B cell precursors and mature B lymphocytes are increased in the BM and spleen of the transgenic mice. Although there is no expansion of the pro-T lymphocyte population in the BM, the number of all major subsets of thymocytes and peripheral T lymphocytes is increased in the majority of the transgenic mice analyzed. The B and T cell lymphocytes in the transgenic mice are functionally competent. In contrast, the number of granulocytes and macrophages in the BM of transgenic mice is similar to that in control non-transgenic littermates. Our results indicate that interleukin 7 plays an important role in vivo in the development of B and T lymphocytes.

Rearrangement patterns of T-cell receptor genes in the spleen of athymic (nu/nu) young mice

Although the athymic nude mouse is grossly deficient in peripheral T cells, the number of lymphocytes bearing T-cell markers (L3T4, LyT2) and the alpha beta or gamma delta T-cell receptor (Tcr) increases steadily with age. The anatomical site(s) where these cells arise are unknown. Splenocytes from 3-5-week-old C57BL/6 (nu/nu) mice contain 2%-5% Pro-T cell progenitors identified with the Joro 37-5 and Joro 75 antibodies, but not mature T cells. To study Tcr gene rearrangement outside the thymus, we fused splenocytes from 3-5-week-old C57BL/6 nude mice with the T-cell lymphoma BW 100.129. Of 22 hybrids that grew stably in culture, four had Tcrd-VD1-D2-J1, two had Tcrd-VD2-J1, and seven had Tcrd-D1-D2 types of rearrangement. Eight hybrids had rearranged the Tcrg-2 gene cluster, but none had rearranged Tcrg-1, -3, or -4. None of the hybrids had rearranged the Tcrb gene cluster and 13 contained DJ rearrangements at the Igh locus. We conclude that the spleen is one of the extrathymic sites where T-cell progenitors can rearranged Tcrd and Tcrg genes. However, there was no evidence for Tcrb gene rearrangements in this organ. Furthermore, the analysis of this limited number of hybrids suggests that extrathymic Tcr gene rearrangements seem to be distinct and much less diverse than those found in the developing thymocytes.

Genetic structure of a soil population of nonsymbiotic Rhizobium leguminosarum

The genetic structure of a population of nonsymbiotic Rhizobium leguminosarum strains was determined by the electrophoretic mobilities of eight metabolic enzymes. Nonsymbiotic strains were isolated from the rhizosphere of bean plants and characterized by growth on differential media and at different temperatures, intrinsic antibiotic resistance, the lack of homology to a nifH probe, and their inability to form nodules on bean roots. All the isolates clustered with R. leguminosarum bv. phaseoli reference strains and did not encompass any other Rhizobium taxa. Their rRNA operon restriction fragment length polymorphisms and the nucleotide sequence of a fragment of the 16S rRNA gene were also found to be identical to those of R. leguminosarum bv. phaseoli reference strains. When complemented with an R. leguminosarum bv. phaseoli symbiotic plasmid (p42d), the nonsymbiotic isolates were able to fix nitrogen in symbiosis with bean roots at levels similar to those of the parental strain. The symbiotic isolates were found at a relative frequency of 1 in 40 nonsymbiotic R. leguminosarum strains.

Thymus colonization in the developing mouse embryo

We have directly followed the formation of and the thymus colonization by pro-T lymphocytes in the developing C57BL/6 mouse embryo by using the monoclonal antibody JORO 37-5 specific for pro-T lymphocytes, immunofluorescence staining and flow fluorocytometry or microscopy analysis. The results show that JORO 37-5+ cells begin to appear in the liver at day 9 of gestation. These JORO 37-5+ cells migrate to and colonize the thymus 1 day later, where they expand vigorously during the next 4-5 days and, subsequently, switch off expression of JORO 37-5 as they further differentiate into mature thymocytes.

Identification and characterization of pro-T lymphocytes and lineage-uncommitted lymphocyte precursors from mice with three novel surface markers

The study of prethymic stages of T cell development has been limited because specific markers for mouse pro-T lymphocytes were not available. We developed a panel of rat monoclonal antibodies (mAbs) that bind to our pro-T lymphocyte clones obtained from bone marrow of young adult mice and the thymus of 14-d-old embryos. The mAbs, called Joro 30-8, Joro 37-5, and Joro 75, were found to bind to all pro-T clones tested but not to cell lines representing later stages of T cell development, B lymphocyte, or myeloid lineages. We determined the frequency and tissue distribution in normal and immunodeficient mouse strains as well as the ontogeny in liver and thymus of cells positive for these mAbs. The results were consistent with the pattern of reactivity observed with cell lines. We isolated Joro 30-8+, Joro 37-5+, and Joro 75+ bone marrow cells by cell sorter and found that: (a) phenotypically, they are Thy-1+, CD4-, CD8-, CD3-, B-220-, IgM-, F4/80-, and PgP-1+; (b) they grew in response to the combination of interleukin 3 (IL-3) + IL-4 or IL-3 + IL-4 + IL-6; and (c) Joro 37-5+ and Joro 75+ marrow cells gave rise to mature T lymphocytes but not to B lymphocytes, while Joro 30-8+ marrow cells generated both T and B lymphocytes after 8-12 wk of transfer into severe combined immunodeficient (Scid) mice. In normal mice subjected to 600 rad of irradiation to induce a wave of thymus recolonization, we found by flow fluorocytometry analysis that Joro+ cells entered the thymus 2 d after irradiation, expanded during the next 4 d, and underwent further differentiation, and from day 8 up to day 21, post-irradiation Joro+ cells were no longer detectable in the thymuses. Immunohistochemical analysis of normal thymus shows the presence of very few Joro 30-8+, Joro 37-5+, and Joro 75+ lymphoid cells in the subcapsular area and outer cortex but not in the medulla. The kinetic analysis of tissue sections from thymuses at various days post-irradiation suggests that Joro+ cells enter the thymus via blood vessels through the subcapsular and outer cortex areas; subsequently, these cells seem to migrate to the inner cortex without reaching the medulla, and give rise to Joro- thymocytes.(ABSTRACT TRUNCATED AT 400 WORDS)

Physical map and properties of a 90-MDa plasmid of Azospirillum brasilense Sp7

Homology was previously detected between the DNA restriction fragments containing Rhizobium meliloti nodulation genes and the 90-MDa plasmid, p90, of Azospirillum brasilense Sp7. Two DNA loci from Sp7 genome that complement mutations in the exopolysaccharide synthesis genes, exoB and exoC, of R. meliloti were also shown to be present on the plasmid. A more detailed characterization of the plasmid was undertaken to establish its physical map and to localize the nod homologies and other specific regions. Six loci were mapped, the region homologous to the nodulation genes, nodPQ, of R. meliloti, the exoB and exoC mutation-correcting loci, a locus for Ap resistance, a bla homology region different from the Ap resistance locus, and a region necessary for the maintenance of p90 as an independent replicon. Mobilization into Agrobacterium tumefaciens of p90-Tn5-Mob was obtained at a frequency of 10(-4), with the plasmid helper pJB3JI. Self-transfer of p90 was not demonstrated. Fragments of p90 hybridized with a plasmid of 90 MDa present in most A. brasilense and some A. lipoferum strains, suggesting a plasmid family in Azospirillum.

Growth factors involved in lymphocyte differentiation

We report here that an interleukin-3-dependent precursor B-cell line, LyD9, differentiated in vitro into mature B cells, producing immunoglobulin (Ig)M and IgG by co-culture with bone marrow stroma cells. Induced LyD9 cells underwent heterogenous immunoglobulin gene rearrangement and synthesized mRNAs encoding immunoglobulin mu (mu), gamma (gamma) and kappa (kappa) chains. LyD9 was also shown to differentiate into myeloid cells. We have established an interleukin-4-dependent derivative clone K-4 that is an intermediate between myeloid-lymphoid cells and the LyD9 clone. This differentiation required direct contact between LyD9 and stromal cells.

LD1: a CD4-CD8- TCR alpha beta/CD3+ peripheral T cell line with helper function for B lymphocytes

In order to learn more about the small subset of CD4-CD8- TCR alpha beta/CD3+ peripheral T lymphocytes, we firstly characterized at the cellular and molecular levels the CD4-CD8- LD1 cell line isolated from the spleen of an MRL/lpr-lpr mouse. Secondly we studied its functional properties. LD1 cells are Thy1+ CD5+ CD4-CD8- LFA-1+ PgP-1+ and do not bind the T cell precursor-specific antibodies Joro 37-5 or Joro 75. They are negative for IgM, B-220, BP-1, J11d, Lyb8, Ia, F4/80, BP-2, and Mac-1 surface markers. LD1 cells have deleted the TCR delta locus, have rearrangements at the TCR gamma gene cluster (i.e. a V gamma 1-J gamma 1-C gamma 1 and a V gamma 4.3-J gamma 4-C gamma 4) and have two rearrangements of the TCR beta gene cluster (i.e. a D beta 1-J beta 1 and V-D-J beta 2). LD1 cells produce normal sized RNA transcripts from TCR alpha and beta genes and lower levels of gamma-mRNA. These cells bind CD3- and pan-TCR beta-specific antibodies as determined by FM analysis. We conclude that LD1 cells bear a TCR alpha beta/CD3 type of receptor complex. LD1 cells fail both in vivo and in vitro to differentiate into CD4+ or CD8+ cells. These cells help B lymphocytes to mature into antibody-secreting cells, secrete IL-3 and IL-6 but not IL-2, IL-4, or IL-5, and exert no detectable cytolytic activity. These results together with recent reports of antigen-specific CD4-CD8- TCR alpha beta/CD3+ cytotoxic T cell lines show that the CD4-CD8- TCR alpha beta/CD3+ subset comprises functionally competent helper and cytotoxic T lymphocytes and thereby argue for their potential to participate in immune responses. Our results also suggest that cells like LD1 represent terminally differentiated T lymphocytes rather than cells with precursor potential for CD4+ or CD8+ TCR alpha beta/CD3+ T lymphocytes.

Thymic epithelial cells induce in vitro differentiation of PRO-T lymphocyte clones into TCR alpha,beta/T3+ and TCR gamma,delta/T3+ cells

PRO-T lymphocyte clones, which have the T cell receptor (TCR) alpha, beta, gamma and delta genes in germline configuration and heterogeneous T cell precursors freshly isolated from bone marrow of athymic nude mice, gave rise to single positive L3T4+ TCR alpha,beta+ and double negative (L3T4-LyT2-) TCR alpha,beta+ or TCR gamma,delta+ cells, but not to any cells expressing LyT2, when co-cultured with the thymic epithelial clone ET. The T cell progenitors were able to develop into cells expressing LyT2 only when cocultured with heterogeneous thymic epithelial cell preparations. The progeny of the induced PRO-T clones included cells bearing V beta 8, V beta 17 and V gamma 3 gene family products. The presence of cells expressing a TCR gamma, delta/T3 receptor complex in the cultures was also documented by the expression of RNA transcripts from the TCR delta and TCR gamma genes by induced PRO-T cells. The TCR/T3+ cells generated in the cultures expressed functionally competent T cell receptor complexes. Our results show that: (i) the same PRO-T clone can give rise to all major subsets of thymocytes upon interaction with the appropriate thymic epithelial cells; (ii) both TCR alpha,beta+ and TCR gamma,delta+ cells may originate from a common T cell progenitor; (iii) L3T4+ TCR alpha, beta+ and L3T4-LyT2- TCR alpha,beta+ cells do not necessarily pass through a L3T4+LyT2+ intermediate stage of development; and (iv) different types of thymic epithelial cells play an essential role in the differentiation of PRO-T cells into either L3T4+ TCR alpha,beta+ L3T4-LyT2- TCR alpha,beta+ or L3T4+LyT2+ and LyT2+ TCR alpha, beta+ cells in vitro. Finally, we have attempted to integrate our results and those of others in a suggested model of T cell development within the thymus.

Monoclonal antibodies reactive with the mouse interleukin 5 receptor

The rat mAbs R52.120 and R52.625 inhibit the action of IL-5 on both IL-5-sensitive cell lines and freshly isolated splenic B lymphocytes. Neither antibody inhibits the proliferative cell responses promoted by IL-2, IL-3, or IL-4. Purified R52.120+ lymphoid spleen cells contain 15-20-fold higher numbers of B lymphocytes responding to IL-5 in the form of maturation into antibody-producing cells. By immunofluorescence staining and flow fluorocytometry, the R52.120 and R52.625 antibodies bound to all 12 IL-5-sensitive cell lines tested. Both antibodies react with 2-4% cells in the spleen, 5% lymphoid cells, and 10-15% myeloid cells in the bone marrow, and 10-14% in the peritoneum of C57BL/6, DBA/2, and BALB/c adult mice. No positive cells for either antibody were detected in the thymus and lymph nodes of these mice. Both R52.120 and R52.625 antibodies specifically inhibit the binding of radiolabeled IL-5 to its receptor. Finally, R52.120 and R52.625 antibodies precipitate from 35S-methionine-labeled IL-5-R+ cell lysates three proteins with Mr 46,000, 130,000, and 140,000. Taken together from these results, we conclude that the R52.120 and R52.625 mAbs recognize epitopes on the IL-5-R complex very close or identical to the IL-5 binding sites.

In vitro effects of recombinant interleukin 7 on growth and differentiation of bone marrow pro-B- and pro-T-lymphocyte clones and fetal thymocyte clones

We have studied the effects of recombinant (r) interleukin 7 (IL-7) on growth and differentiation of marrow pro-B-lymphocyte clones (CB/Bm7, LyD9, LyB9), marrow pro-T-lymphocyte clones (C4-77/3, C4-86/18, C4-95/16), and fetal thymocyte clones (FTH5, FTA2, FTD5) in the presence or absence of the bone marrow stroma clone RP.0.10, which was selected for its ability to promote differentiation of the pro-B clones. rIL-7 alone stimulated some DNA synthesis (measured by [3H]thymidine uptake) but not actual growth (increase in cell number) of the pro-B clones. Antibodies against IL-4 and IL-6 or against receptors for IL-2, IL-3, and IL-5 did not inhibit this effect of rIL-7 on the pro-B clones. rIL-7 alone or in various combinations with other cytokines (from rIL-1 alpha to rIL-6) could not induce differentiation of the pro-B clones into IgM+ B cells regardless of the presence of lipopolysaccharide (LPS). The RP.0.10 marrow stroma cells by themselves do not support the growth of the pro-B clones. However, the pro-B clones grew when cultured with rIL-7 and monolayers of the RP.0.10 stroma cells. While the RP.0.10 stroma cells induced the pro-B clones to differentiate into IgM+ B cells but not T3+ T cells when cultured in the presence of LPS and rIL-3, the B-cell progenitor clones gave rise to significantly higher numbers of IgM+ B cells (up to 63%) and to many more B cells expressing higher levels of surface IgM when cocultured with rIL-7, LPS, and RP.0.10 stroma cells. The pro-B clones also generated IgM+ B cells (up to 20%) when cocultured with RP.0.10 stroma cells and rIL-7 in the absence of LPS. By using culture plates designed for testing requirements for cell-cell contact, we found that cell interactions between the pro-B cell and the marrow stroma cell are essential to induce rearrangement and expression of the immunoglobulin genes in the pro-B clones. Possible mechanisms to account for the remarkable effects of rIL-7 in the presence of RP.0.10 stroma cells on both growth and differentiation of the pro-B clones are discussed. Finally, rIL-7 alone or together with RP.0.10 stroma cells neither supported proliferation nor induced differentiation into T3+ T cells or IgM+ B cells of the marrow pro-T clones or the fetal thymocyte clones. In light of these findings, we postulate that the interaction of the pluripotential stem cell with marrow stroma cells like RP.0.10 and the availability of IL-7 could play a critical role in the commitment to develop along the B-lymphocyte pathway.

The epigenetic influences of bone marrow and fetal liver stroma cells on the developmental potential of Ly-1+ pro-B lymphocyte clones

The Ly-1+ Mac-1+ B-220+ CC11+ progenitor clones LyD9 and LyB9 were previously shown to give rise to Ly-1+IgM+ B lymphocytes either in vivo or in vitro by co-culture with nonlymphoid accessory cells from spleen and lipopolysaccharide. The clones did not generate T lymphocytes either in vivo or in vitro. We now find that both LyD9 and LyB9 progenitors are induced to differentiate in vitro by co-culture with the RP.0.10 bone marrow stroma clone or with heterogeneous marrow-adherent stroma cell populations obtained from adult mice into Ly-1-IgM+ B lymphocytes as well as myeloid GM1.2+ Mac-1+ cells. We could obtain evidence that a high proportion of LyD9 and LyB9 cells already switched off expression of Ly-1 and CC11 (interleukin 3 receptor) surface molecules 2 days after initiation of the cultures, and by days 8-10 of culture no detectable Ly-1+ cells and only about 20% CC11+ cells were observed. Ly-1 surface expression could not be re-induced on the progeny of LyD9 and LyB9 progenitors generated under the influence of marrow stroma cells. Remarkably, the LyD9 and LyB9 progenitors gave rise to both Ly-1+IgM+ and Ly-1-IgM+ B cells upon culture with heterogeneous stroma monolayers obtained from 18-day fetal liver. Finally, the differentiating property of the stroma cells for the LyD9 and LyB9 progenitors could not be replaced with soluble factors produced either spontaneously or after stimulation by the marrow stroma cells. Our results show the importance of epigenetic influences provided by a given microenvironment on the developmental potential of B cell progenitors. They provide direct evidence that the same pro-B lymphocyte can give rise to both Ly-1+ and Ly-1-IgM+ B cells depending on both the time of development and the tissue of origin of stroma cells with which the B cell progenitor interacts. Also, the results strongly suggest that cell contact between the stroma cell and the B cell progenitor is essential to induce rearrangement and expression of the Ig genes in pro-B lymphocytes.

Expression of the p75 interleukin 2-binding protein on CD3+4-8-Tac- cells from autoimmune MRL/MP-lpr/lpr mice

The recently described (Sharon, M. et al., Science 1986. 234:859) interleukin 2 (IL 2)-binding molecule p75 was detected in the CD3+4-8-Tac- "double-negative" cell population selectively expanded in lupus-like autoimmune mice MRL/MP-lpr/lpr using cross-linking studies. Scatchard analysis of the IL 2 binding revealed the existence of approximately 4700 sites per cell with an apparent Kd of 1500 pM. The cell line LD1.T3B, derived from this population, shared surface markers and the p75 presence/p55 absence of IL 2-binding proteins with its in vivo counterpart, displaying around 3100 sites per cell with a Kd of about 1300 pM. Functional studies showed that high doses of IL 2 had an inhibitory effect on the autonomous growth of this cell line in the absence of the development of killer activity. This study provides evidence of the functional abilities of p75, and shows that the use of Tac/p55 surface expression only to evaluate IL 2 receptors and T cell activation can be an oversimplification as well as misleading.

An interleukin-4-dependent precursor clone is an intermediate of the differentiation pathway from an interleukin-3-dependent precursor clone into myeloid cells as well as B lymphocytes

An interleukin-3-dependent progenitor clone LyD9 and its interleukin-4-dependent derivative clone K-4 were shown to differentiate into myeloid cells as well as B lymphocytes by coculture with bone marrow stroma cells. The K-4 clone is an intermediate between myeloid/lymphoid cells and the LyD9 clone that requires interleukin-4 for differentiation into B lymphocytes and myeloid cells. Granulocyte-macrophage colony stimulating factor-dependent derivatives (LS-1 and K-GM) were also established from induced LyD9 cells. LS-1 and K-GM were myeloid-committed cells.

Thymocyte clones from 14-day mouse embryos. II. Transcription of T3 gamma gene may precede rearrangement of TcR delta and expression of T3 delta, T3 epsilon and T11 genes

We have studied the state of TcR delta gene and the expression of T3 delta, T3 epsilon, T3 gamma and T11 (CD2) genes in the fetal thymocyte (FT) clones A2, G15, H5, E10, D5, H12, F1 and D11 obtained from a 14-day B10.BR mouse fetal thymus. The eight FT clones contain the TcR delta gene in the germ-line configuration as determined by Southern blot analysis. With the exception of clones E10 and D5, the other six FT clones express normal sized transcripts for T3 gamma gene and none of the eight FT clones produced detectable RNA transcripts for T3 delta, T3 epsilon and T11 genes as assessed by Northern blot analysis. Together with our previous work showing that all eight FT clones contain the TcR gamma and the TcR beta gene clusters in the germ-line configuration, the data indicate that the FT clones represent the earliest stage of T cell development identified within the thymus. Our results provide evidence that (a) the T3 gamma gene is the first of the genes that encode components of a TcR/T3 complex to be expressed in ontogeny within the thymus; (b) the T3 (delta, epsilon, gamma) genes are switched on asynchronously and their expression must be differentially regulated, and (c) the T11 gene product may not be involved in early stages of T cell development within the thymus.

Differentiation of an interleukin 3-dependent precursor B-cell clone into immunoglobulin-producing cells in vitro

Precursors to B-cell lines with immunoglobulin genes in the germ-line context have been shown to be capable of generating mature B cells in vivo. We report here that an interleukin 3-dependent precursor B-cell line, LyD9, differentiated in vitro into mature B cells, producing IgM and IgG by coculture with bone marrow accessory (or stroma) cells or with dendritic cells and T cells. Up to 50% of IgM-positive cells, but no Thy-1-positive cells, appeared after the 7- to 10-day coculture. Induced LyD9 cells underwent heterogenous immunoglobulin gene rearrangement and synthesized mRNAs encoding immunoglobulin mu, gamma, and kappa chains. However, these cells did not show any rearrangement of genes encoding the alpha and beta chains of the T-cell receptor. The induction of differentiation by coculture with bone marrow stroma cells was blocked by anti-lymphocyte function-associated antigen 1 or anti-interleukin 4 antibody. These systems are useful for molecular biological studies on regulation of differentiation of bone marrow-derived cells into the B-cell lineage.

Narrow- and Broad-Host-Range Symbiotic Plasmids of Rhizobium spp. Strains That Nodulate Phaseolus vulgaris

Agrobacterium transconjugants containing symbiotic plasmids from different Rhizobium spp. strains that nodulate Phaseolus vulgaris were obtained. All transconjugants conserved the parental nodulation host range. Symbiotic (Sym) plasmids of Rhizobium strains isolated originally from P. vulgaris nodules, which had a broad nodulation host range, and single-copy nitrogenase genes conferred a Fix + phenotype to the Agrobacterium transconjugants. A Fix − phenotype was obtained with Sym plasmids of strains isolated from P. vulgaris nodules that had a narrow host range and reiterated nif genes, as well as with Sym plasmids of strains isolated from other legumes that presented single nif genes and a broad nodulation host range. This indicates that different types of Sym plasmids can confer the ability to establish an effective symbiosis with P. vulgaris.

Genomic instability in Rhizobium phaseoli

Experience from different laboratories indicates that Rhizobium strains can generate variability in regard to some phenotypic characteristics such as colony morphology or symbiotic properties. On the other hand, several reports suggest that under certain stress conditions or genetic manipulations Rhizobium cells can present genomic rearrangements. In search of frequent genomic rearrangements, we analyzed three Rhizobium strains under laboratory conditions that are not considered to cause stress in bacterial populations. DNAs from direct descendants of a single cell were analyzed in regard to the hybridization patterns obtained, using as probes different recombinant plasmids or cosmids; while most of the probes utilized did not show differences in the hybridization patterns, some of them revealed the occurrence of frequent genomic rearrangements. The implications and possible biological significance of these observations are discussed.

Analysis by in situ hybridization of cells expressing mRNA for interleukin 4 in the developing thymus and in peripheral lymphocytes from mice

We have made use of RNA.RNA in situ hybridization to study the presence of cells producing mRNA for interleukin 4 (IL-4) in the developing thymus, spleen, and T-cell line 2.19. Approximately 1 of 300-400 spleen cells expressed detectable IL-4 mRNA 24 hr after their stimulation by the lectin concanavalin A. Spleen cells were also induced to express mRNA for IL-4 by stimulation with alloantigens. Splenocytes producing mRNA for IL-4 were detected 4 hr after stimulation by concanavalin A; the response peaked at approximately equal to 24 hr and was undetectable by 72 hr. Cyclosporin A inhibited the synthesis of IL-4 mRNA in the T-cell line 2.19, which had been induced by concanavalin A. Approximately 1 of 10 fetal thymocytes at day 14 of gestation expressed mRNA for IL-4 after their stimulation by phorbol 12-myristate 13-acetate and ionomycin. Both the frequency of fetal thymocytes expressing IL-4 mRNA and the amount of mRNA for IL-4 synthesized per cell sharply decreased at day 16 of gestation, and less than 1 of 1800 fetal thymocytes at day 18 of gestation expressed detectable IL-4 mRNA. Our results define the relative frequency of cells capable of expressing IL-4 mRNA after stimulation in vitro in the spleen and in the developing thymus. The data strongly argue for an important role of IL-4 in growth and differentiation of lymphoid cells, notably during T-cell development within the thymus.

Ly1+ PRO-B lymphocyte clones. Phenotype, growth requirements and differentiation in vitro and in vivo

Several clones obtained from the bone marrow of a BALB/c mouse were found to contain the heavy and light chain Ig genes in the germline configuration, to express Ly1 and to carry the B cell lineage markers B-220, Lyb8 and BP-1; these clones are Pgp-1+, LFA-1+, J11d+, Mac-1+ and Thy1-, Lyt2-, L3T4-, GM1.2- and Ia-. Three clones analyzed in detail (Lyd9, LyH7 and Lyb9) have receptors for interleukin (IL) 2 and IL3 as assessed with the 7D4 and CC11 monoclonal antibodies respectively. They grow in rIL3 but not in rIL2 or rIL1; both rIL4 and rIL5 also promote their proliferation, albeit to a much lesser extent than rIL3. None of the interleukins tested alone or in various combinations promoted the clones to differentiate in vitro along the B cell pathway. Treatment with 5-Azacytidine (5-Aza) induced cell surface Ia expression but not rearrangement or expression of Ig genes. However, 5-Aza-treated Lyd9, LyH7 and Lyb9 cells co-cultured with X-ray irradiated accessory cells and LPS gave rise to Ly1+, IgM+ B lymphocytes (range 14-51%) including mu + kappa + (78-93%), and mu + lambda + (9-25%) B lymphocytes. In vivo, the Lyd9, LyH7 and Lyb9 clones gave rise to IgM+ B lymphocytes (8.5-17%) including mu + kappa +, and mu + lambda +, but not to Lyt2+ or L3T4+ T lymphocytes after 4-6 weeks of transfer into Scid mice. Our results indicate that Ly1+ IgM+ cells comprise a subpopulation of B lymphocytes that is derived from IL3-responsive Ly1+ PRO-B lymphocytes.

Reiterated DNA sequences in Rhizobium and Agrobacterium spp

Repeated DNA sequences are a general characteristic of eucaryotic genomes. Although several examples of DNA reiteration have been found in procaryotic organisms, only in the case of the archaebacteria Halobacterium halobium and Halobacterium volcanii [C. Sapienza and W. F. Doolittle, Nature (London) 295:384-389, 1982], has DNA reiteration been reported as a common genomic feature. The genomes of two Rhizobium phaseoli strains, one Rhizobium meliloti strain, and one Agrobacterium tumefaciens strain were analyzed for the presence of repetitive DNA. Rhizobium and Agrobacterium spp. are closely related soil bacteria that interact with plants and that belong to the taxonomical family Rhizobiaceae. Rhizobium species establish a nitrogen-fixing symbiosis in the roots of legumes, whereas Agrobacterium species is a pathogen in different plants. The four strains revealed a large number of repeated DNA sequences. The family size was usually small, from 2 to 5 elements, but some presented more than 10 elements. Rhizobium and Agrobacterium spp. contain large plasmids in addition to the chromosomes. Analysis of the two Rhizobium strains indicated that DNA reiteration is not confined to the chromosome or to some plasmids but is a property of the whole genome.

Thymocyte clones from 14-day mouse embryos. I. State of T cell receptor genes, surface markers, and growth requirements

We have established in culture 13 clones from the thymus of a 14-d B10.BR mouse embryo and characterized 8 of them. All eight FT clones have the TCR-gamma and -beta genes in germline configuration. They express mRNA for the gamma, but not for the beta nor the alpha genes. All eight FT clones are Thy-1+, Ly-1+, LFA-1+, Pgp-1+, H-2K+, and T3-. Three phenotypes could be distinguished on the basis of Lyt-2, L3T4, and IL-2-R expression: Lyt-2+, L3T4-, IL-2-R+ (I); Lyt-2+, L3T4-, IL-2-R- (II); and Lyt-2+, L3T4+, IL-2-R+ (III) cells. All eight clones grow in rIL-4 and six clones also proliferate in rIL-2. Antibodies specific for IL-2-R inhibit their response to rIL-2 but not to rIL-4. The eight FT clones synthesize mRNA for IL-4 after stimulation in vitro and none of them exhibit cytolytic activity or helper function for B lymphocytes. We conclude that the FT clones are at a very early stage of T cell development, that the expression of Lyt-2 and L3T4 surface molecules can precede that of the antigen receptor, and that the same fetal thymocyte can use both IL-4 and IL-2 as growth factor.

Molecular, cellular, and functional properties of bone marrow T lymphocyte progenitor clones

The continuous proliferating bone marrow clones C4-77, C4-86, and C4-95 express low levels of Thy-1 and Ly-1 surface antigens, but no detectable surface antigens normally present on thymocytes, peripheral mature T lymphocytes, cells of the B lymphocyte or myeloid lineages. They contain the T cell antigen receptor genes alpha, beta, and the T cell-specific gene gamma in the germline configuration, and they express functional receptors for IL-3 and nonfunctional receptors for IL-2. The C4 clones are able to home and undergo differentiation in the thymus of sublethally irradiated mice and give rise in vivo to phenotypically and functionally mature peripheral T lymphocytes displaying several antigen specificities. In vitro 5-Azacytidine induces the C4 clones to express Lyt-2 and L3T4 T cell differentiation antigens, and renders them amenable to be switched from IL-3 to IL-2 dependence. However, the C4 clones seem incapable of giving rise to B lymphocytes either in vivo or in vitro. They self-renew in vitro in the presence of IL-3 every 12-14 h. We conclude that the C4 clones represent cells at the earliest stage of T cell development, i.e., Pro-T lymphocytes.

Nitrogen-fixing nodules induced by Agrobacterium tumefaciens harboring Rhizobium phaseoli plasmids

Rhizobium phaseoli CFN299 forms nitrogen-fixing nodules in Phaseolus vulgaris (bean) and in Leucaena esculenta. It has three plasmids of 185, 225, and 410 kilobases. The 410-kilobase plasmid contains the nitrogenase structural genes. We have transferred these plasmids to the plasmid-free strain Agrobacterium tumefaciens GMI9023. Transconjugants containing different combinations of the R. phaseoli plasmids were obtained, and they were exhaustively purified before nodulation was assayed. Only transconjugants harboring the 410-kilobase plasmid nodulate P. vulgaris and L. esculenta. Nodules formed by all such transconjugants are able to reduce acetylene. Transconjugants containing the whole set of plasmids from CFN299 nodulate better and fix more nitrogen than the transconjugants carrying only the Sym plasmid. Microscopic analysis of nodules induced by A. tumefaciens transconjugants reveals infected cells and vascular bundles. None of the A. tumefaciens transconjugants, not even the one with the whole set of plasmids from CFN299, behaves in symbiosis like the original R. phaseoli strain; the transconjugants produce fewer nodules and have lower acetylene reduction (25% as compared to the original R. phaseoli strain) and more amyloplasts per nodule. More than 2,000 bacterial isolates from nodules of P. vulgaris and L. esculenta formed by the transconjugants were analyzed by different criteria. Not a single rhizobium could be detected. Our results show that R. phaseoli plasmids may be expressed in the A. tumefaciens background and direct the formation of effective, differentiated nodules.

Bone marrow pro-T and pro-B lymphocyte clones express functional receptors for interleukin (IL) 3 and IL 4/BSF-1 and nonfunctional receptors for IL 2

It is shown here that the C4-77 and C4-86 bone marrow clones with properties of pro-T lymphocytes and the Bc/Bm11 and CB/Bm7 clones with characteristics of pro-B lymphocytes grow in recombinant interleukin 4 (rIL4)/BSF-1 and IL3, but not in rIL2. The proliferative cell responses to rIL4/BSF-1 were always less that approximately 50% of those achieved by the clones in response to IL3. The CC11 monoclonal antibody (mAb) specific for IL3-sensitive mouse cells did not affect the action of rIL4/BSF-1, but it did inhibit the action of IL3 on the clones. The PC61 mAb against IL2 receptors had no effect on either rIL4/BSF-1- or IL3-driven responses. All four clones carry on the cell membrane the glycoproteins recognized by the CC11 mAb and by the PC61 mAb as assessed by immunofluorescence staining and flow cytometry. We conclude that the pro-T and the pro-B clones express functional receptors for IL3 and rIL4/BSF-1 and nonfunctional receptors for IL2, that rIL4/BSF-1 promotes growth of these clones via an IL3- and IL2-independent pathway and discuss the possible biological significance of these findings.

Recombinant interleukin 4/BSF-1 promotes growth and differentiation of intrathymic T cell precursors from fetal mice in vitro

Recombinant mouse interleukin 4/BSF-1 (rIL4/BSF-1) together with phorbol myristate acetate (PMA) promotes growth of one out of approximately four intrathymic T cell precursors from fetal mice (14-15 days gestation). This response is not inhibited by even high concentrations of monoclonal antibody against the receptor for interleukin 2. Fetal thymocytes activated by rIL4/BSF-1 plus PMA give rise to cytolytic T cells after 7-21 days of culture. All the proliferating cells are Thy1+, some of them express Lyt2 but none has detectable L3T4 T cell differentiation antigens nor T cell antigen receptor (F23.1) on the cell membrane as assessed by immunofluorescence staining and flow fluorocytometry analysis. It is concluded that rIL4/BSF-1 exerts both growth and differentiation activities on normal intrathymic T cell precursors. The results provide evidence for an alternative growth factor to interleukin 2 involved in proliferation of T cell precursors. These findings open new and direct ways of studying cellular and molecular events during the differentiation of normal intrathymic T cell precursors in vitro and extend the spectrum of target cells for IL4/BSF-1.

Abelson virus abrogation of interleukin-3 dependence in a lymphoid cell line

Among several tyrosine-protein kinases, only v-abl could abrogate interleukin 3 dependence of a lymphoblastoid cell line; v-src and v-fps proteins gave partial or no interleukin 3 independence, respectively. Lymphokine independence was achieved via a nonautocrine mechanism. Direct involvement of c-myc in this process was not evident.

Splenocytes and bone marrow cells from T-cell deficient Nu/Nu mice secrete interleukin 3 activity after stimulation in vitro

We show here that the combination of Concanavalin A (Con A), phorbol myristate acetate (PMA), and Ionomycin (Iono) reproducibly stimulated splenocytes from Nu/Nu mice and bone marrow cells from both normal and Nu/Nu mice to secrete interleukin 3 (IL-3) in vitro. IL-3 was measured by its property of supporting the growth of four different clones known to grow only in IL-3. None of the agents indicated above nor several other types of stimuli tested could induce the cells to secrete IL-3 activity. IL-3 activity from induced cells of either tissue was detected after 24 hr of culture, peaked at 48 hr and either declined by 72-96 hr of culture (bone marrow cells) or remained relatively constant through the 4-day culture period (splenocytes). The cells participating in the production of IL-3 activity in Nu/Nu spleen were THY1+, L3T4-, LyT2-, B-220-, J11d-, Ia-, and those in the marrow from either normal or Nu/Nu mice were THY1+, J11d+, L3T4-, LyT2-, B-220-, Ia-. Finally, we present evidence that Ia-positive cells negatively regulate the production of IL-3 activity by both splenocytes and marrow cells. We conclude that Nu/Nu splenocytes and bone marrow cells from both normal and Nu/Nu mice can secrete IL-3 activity after proper stimulation in vitro and that such property is negatively regulated by Ia-positive cells.

Monoclonal antibodies specific for interleukin 3-sensitive murine cells

The mAb CC11 and CB5 reacted against all 18 IL-3-dependent cell lines tested, but not against cells insensitive to IL-3. Up to 53% nucleated cells from fetal liver (14th day of gestation) and 79% bone marrow cells of young adult mice were positive for both CC11 and CB5 antigens, but cells from thymus, lymph node, heart, and kidney were negative. The molecule recognized by both antibodies has an Mr of 50,000-70,000, a pI of 5.7-6.2, and carries heterogeneous N-linked glycans of high Mr. Both CC11 and CB5 specifically inhibited the growth of clones supported by rIL-3. Neither antibody affected the action of IL-1, IL-2, or B cell maturation factor; the proliferative responses of splenocytes to Con A, PWM, and LPS; nor the maturation of spleen B cells into antibody-secreting cells stimulated by LPS. rIL-3 specifically modulated the expression of the CC11/CB5 glycoprotein on the cell membrane of IL-3-dependent clones. Finally, freshly isolated bone marrow cells that have the CC11/CB5 glycoprotein on the cell membrane proliferated in response to IL-3, whereas cells that lack this molecule did not. We suggest that CC11 and CB5 react against receptors for mouse IL-3.

Requirements for growth of immature thymocytes from fetal and adult mice in vitro

We report here defined culture conditions that allow reproducibly the growth of the majority of immature thymocytes from both fetal (14-15 days of gestation) and adult mice. The combination of phorbol myristate acetate (PMA), ionomycin and recombinant interleukin 2 (IL2) is both sufficient and necessary to induce growth of about 1/6.2 (range 1/3-1/9) and 1/4.3 (range 1/2-1/7) immature thymocytes from adult and fetal mice, respectively, in serum-free cultures. Several other combinations tested (e.g. PMA + IL2, concanavalin A + IL2) were poorly or not active. None of the agents tested alone (PMA, ionomycin, concanavalin A, pokeweed mitogen, IL2) had any effect. We found no evidence for a role of IL1 and IL3 on growth of these cells. The growth of activated immature thymocytes from either fetal or adult mice was inhibited by a monoclonal antibody against mouse IL2 receptors. Under the same conditions that stimulated growth of most immature thymocytes, they did not mature into cells expressing Lyt-2, L3T4 or T cell antigen receptor (KJ16) after 7 to 15 days of continuous proliferation in culture. Nor did they give rise to cells with cytolytic activity after 7-9 days of culture. In some but not all experiments cultures of immature thymocytes from adult mice but not from fetal mice generated cells (1 out of 120-310) with helper function for B lymphocytes. While we confirmed here that approximately 50-70% freshly isolated immature thymocytes express receptors for IL2, our results indicate that these cells need to be activated (by e.g. PMA + ionomycin) to respond to IL2. A possible mechanism to account for the expression of nonfunctionally competent IL2 receptors is proposed and our results concerning the maturation of immature thymocytes in vitro are discussed.

Monoclonal antibodies against human Ia antigens stimulate monocytes to secrete interleukin 1

The monoclonal antibodies (mAb) DA6.147, DA6.164, and HIG.48 against human Ia antigens, but not the W6/32 mAb against human class I major histocompatibility complex antigens or the anti-monocyte OKM1 and 63D3 mAb, stimulated monocytes to secrete interleukin 1 (IL-1). IL-1 was measured by its property of promoting the production of interleukin 2 (IL-2) by phytohemagglutinin-treated LBRM-33 clone 1A5 cells. IL-1 activity induced by anti-Ia antibodies could be detected 24 hr after initiation of the cultures and reached its highest levels at days 3-4 of culture. Concentrations of 1 microgram/ml or higher of the anti-Ia antibodies induced monocytes to secrete significant levels of IL-1 activity. The anti-Ia mAb induced Ia-bearing but not Ia-negative monocytes to secrete IL-1. Both Ia-positive and Ia-negative monocytes produced IL-1 activity under the stimulus of lipopolysaccharide. It is concluded that the DA6.147, DA6.164, and HIG.48 mAb stimulate secretion of IL-1 by interacting Ia antigens on monocytes. The data support the view that besides serving as restricting elements for recognition of foreign antigens by T cells, Ia antigens may also function as transducer elements.

Both cloned interleukin 2 and purified interleukin 1 are required for optimal growth of purified L3T4+ and Lyt 2+ lymphocytes initiated by concanavalin A

Concanavalin A (Con A), cloned interleukin 2 (IL-2), purified interleukin 1 (IL-1) or two different crude preparations containing IL-1 activity alone, did not induce proliferation of rigorously accessory cell (AC)-depleted splenic L3T4+ or Lyt 2+ lymphocytes. Con A together with saturating concentrations of cloned IL-2 (100 U/ml) promoted less than 40% of the proliferative responses observed in AC-supplemented L3T4+ and Lyt 2+ T-cell cultures. The three preparations of IL-1 used supported minimal proliferation of Con A-treated purified L3T4+ or Lyt 2+ lymphocytes. However, all these IL-1 preparations promoted significant growth of the T-cell populations if AC (1%) were included in the cultures. Cloned IL-2 combined with purified IL-1 promoted proliferation of Con A-treated L3T4+ and Lyt 2+ lymphocytes achieving approximately 75% of the responses observed in AC-supplemented T-cell cultures. The additive effect of IL-1 was apparent in the presence of saturating concentrations of cloned IL-2. Finally, Con A alone induced a detectable number of both L3T4+ and Lyt 2+ lymphocytes to express IL-2 receptors as determined with the anti-mouse IL-2 receptor antibody 7D4 by immunofluorescence and FACS analysis. Purified IL-1 neither induced detectable number of L3T4+ or Lyt 2+ T cells to express IL-2 receptors nor increased the number of Con A-treated T cells bearing IL-2 receptors. We have interpreted these findings to indicate the following: Con A alone is sufficient to induce highly purified L3T4+ and Lyt 2+ lymphocytes to express IL-2 receptors. Cloned IL-2 and purified IL-1 are required for optimal growth of L3T4+ and Lyt 2+ lymphocytes and these cytokines together efficiently replace AC in growth of T cells initiated by Con A. IL-1 alone does not replace AC in Con A-induced activation of mouse T cells. IL-1 exerts potentiation on IL-2-driven growth of Con A-treated L3T4+ and Lyt 2+ lymphocytes. The additive activity of IL-1 on growth of normal T cells is not due to increased production of IL-2 in the cultures or induction of normal T cells to expression of IL-2 receptors by IL-1. We propose that IL-1 optimizes the action and/or interaction of IL-2 with its receptors on the T-cell membrane (by, i.e., increasing affinity of the IL-2 receptor for its ligand and/or stabilizing the IL-2 receptor).

Mechanisms by which accessory cells contribute in growth of resting T lymphocytes initiated by OKT3 antibody

This study was undertaken to determine how accessory cells (AC) participate in growth of normal resting T cells initiated by anti-T3 monoclonal antibodies. Highly purified peripheral blood resting T cells were obtained by sequentially using three procedures (adherence to plastic surface, adherence to nylon wool columns and treatment with four monoclonal antibodies against antigens on AC and activated T cells plus complement). The assays for T cell growth were carried out at low cell density (10(4) cells/well) and with T cell populations where we could not detect cells bearing OKM1 and Ia antigens. Soluble OKT3 antibody, concanavalin A, recombinant interleukin 2 (IL 2) or purified interleukin 1 (IL 1) alone did not induce proliferation of purified resting T cells. Recombinant IL2 together with soluble OKT3 antibody stimulated significant growth whereas purified IL1 and two distinct preparations derived from AC containing IL 1 activity did not. Nevertheless, purified IL 1 amplified the proliferation of T cells induced by soluble OKT3 antibody in the presence of a small number of irradiated AC (3%). Phorbol myristate acetate (PMA) together with soluble OKT3 antibody activated purified resting T cells to proliferate, but PMA alone had little growth-promoting activity only. Soluble OKT3 antibody did not by itself induce a detectable number of resting T cells to express receptors for IL2 as determined by direct immunofluorescence staining and FACS analysis with monoclonal anti-IL2 receptor antibody. Cloned IL2 or purified IL1 alone did not induce resting normal T cells to express receptors for IL2 either. In contrast, T cells exposed to both soluble OKT3 antibody and IL2 exhibited IL2 receptors. PMA alone stimulated some resting T cells to express IL2 receptors and this response was significantly increased when the drug was used together with soluble OKT3 antibody. Studies were performed with unfractionated mononuclear cells from a donor whose cells respond to OKT3 (IgG2) but not to Leu 4 (IgG1) anti-T3 antibodies. Recombinant IL 2 but not purified IL 1 corrected the defective response to Leu 4 antibody. Finally, OKT3 antibody linked to beads, but not in soluble form, and purified IL1 replaced AC in growth of purified resting T cells. Based on these data I conclude the following: (a) AC participate in growth of resting normal T cells initiated by anti-T3 antibodies through their Fc receptors in two ways, namely, by providing a matrix to favour cross-linking of the T3 complex and simultaneously by secreting IL1.(ABSTRACT TRUNCATED AT 400 WORDS)

Il-3-dependent mouse clones that express B-220 surface antigen, contain Ig genes in germ-line configuration, and generate B lymphocytes in vivo

The continuously proliferating clones L/B AgA2, CB/Bm 7, Ba/C1, and Bc/Bm 11 were established from bone marrow of MRL/LPR, CBA/J, and BALB/c mice. These clones carry the B cell lineage surface antigen B-220 but not antigens normally expressed on mature B lymphocytes, myeloid cells, or T lymphocytes. Their immunoglobulin mu heavy chain and kappa light chain genes are in germ-line configuration. The G418 resistance gene was introduced into each clone with a retrovirus vector and then used as a selective marker for the progeny of transfected cells. Clones L/B AgA2, CB/Bm 7, and Bc/Bm 11, but not Ba/C1, could develop into antibody-secreting cells after in vivo transfer. None gave rise to cells responsive to polyclonal T cell activators, nor did any differentiate into cells that could develop into granulocyte/macrophage-colony-forming cells in vitro. All grew in interleukin 3 but not in other cytokines. We conclude that clones L/B AgA2, CB/Bm 7, and Bc/Bm 11 are early precursors of B lymphocytes.

Cyclosporin A inhibits antigen- and lectin-induced but not constitutive production of interleukin 3

Cyclosporin A (CyA) strongly inhibited production of interleukin 3 (IL3) by normal mouse spleen cells and by the T lymphoma LBRM-33 clone 1A5 induced by alloantigens and by the lectins concanavalin A or phytohemagglutinin. At the same concentrations at which CyA exerted this suppressor activity, it did not affect the growth of the Ea3.15 pre-B cell clone supported by recombinant mouse IL3 (the read-out for IL3 activity used in this study) nor did it show significant inhibitory effect on the spontaneous secretion of IL3 by WEHI-3 cells and by the LD1 T helper line. Taken together, these observations indicate that CyA does not interfere with translation, synthesis or secretion of IL3. CyA most likely interferes with the process by which antigens and lectins induce transcription of genes coding for lymphokines.

Spontaneous production of interleukin 3 by T lymphocytes from autoimmune MRL/MP-lpr/lpr mice

MRL/MP-lpr/lpr (MRL/lpr) mice develop a lupus-like autoimmune disease and a massive generalized lymphadenopathy associated with proliferation of nonmalignant Thy-1+ Lyt-1+ cells. The mechanism(s) leading to outgrowth of these cells is unknown. We report here that Thy-1+, Lyt-1+, Lyt2- lymphocytes from spleens of MRL/lpr mice, but not from several strains of normal mice, spontaneously secrete IL3. The presence of IL3 is shown by: (a) the ability of the supernatants from unstimulated spleen cells of MRL/lpr (MRL/lpr SUP) to support growth of IL3 but not IL2 addicted cells and (b) the growth-promoting activity in MRL/lpr SUP was absorbed with IL3-dependent cells but not with IL2-dependent cells. Spontaneous release of IL3 was detected in supernatants from spleen cells of 6-week-old MRL/lpr mice and the titers of IL3 activity increased with age. Nylon wool-enriched cells from spleens of MRL/lpr mice proliferated in response to purified IL3 and IL3 secreted by MRL/lpr T cells, in a manner similar to nylon wool-passed cells from normal mice. The cells responding to both sources of IL3 were Thy-1+, Lyt-1+, Lyt-2-. Thus, Thy-1+, Lyt-1+,2- cells from spleen of MRL/lpr mice spontaneously secrete IL3 and respond normally to this lymphokine. Four Thy-1+, Lyt-1+,2- cell lines derived from unstimulated spleen cells of MRL/lpr mice were established in culture with IL3. These IL3-sensitive T cell lines help syngeneic and H-2 compatible normal small "resting" B cells to mature into plasma cells secreting predominantly IgG1, IgG2 and IgA. Taken together, these data and previous findings that T cells from MRL/lpr mice have an impaired production of and response to IL2, strongly suggest that abnormal production of IL3 may account for the outgrowth of Thy-1+, Lyt-1+,2- cells in the MRL/lpr mouse. Finally, a mechanism linking abnormal production of IL3 and B cell hyperactivity in these animals is proposed.

Interleukin-3 supports growth of mouse pre-B-cell clones in vitro

Study of the differentiation of immunoglobulin-producing B lymphocytes has been hampered by the inability to maintain homogeneous populations of precursor cells in vitro. We describe here that interleukin-3 supports the growth of freshly isolated fetal liver pre-B cells and the long-term culture of interleukin-3 dependent pre-B-cell clones that can be induced to mature into antibody secreting cells in vitro.

Immunologic evaluation of T chronic lymphocyte leukaemia cells in a patient with a concomitant IgA2 myeloma

Peripheral blood lymphocytes from a patient with OKT3, OKT4, OKT17 positive T CLL and a concomitant IgA2/lambda myeloma were found to be suppressive in cocultivation experiments and after in vitro preactivation . Although chromosomal analysis after stimulation with T or B cell mitogens suggested a common origin of the two malignancies, T cells did not carry structures recognized by an anti-idiotypic antiserum raised against the purified M-component. Only Fc mu receptors were found on the T cells with conventional rosetting assays, although a weak binding of Latex particles coated with the purified IgA M-component could occasionally be recorded. When purified T cells were submitted to FACS-analysis after incubation with the FITC-conjugated purified M-component, two subsets could easily be distinguished in normal T cells, whereas only the high affinity-binding subset could be found in the patient.