An idiotype-specific helper population that bears immunoglobulin, Ia, and Lyt-1 determinants

Signal transducer and activator of transcription-3 (STAT3) is constitutively activated in normal, self-renewing B-1 cells but only inducibly expressed in conventional B lymphocytes

Cytokine and growth factor receptor engagement leads to the rapid phosphorylation and activation of latent, cytosolic signal transducers and activators of transcription (STAT) proteins, which then translocate to the nucleus where they regulate transcriptional events from specific promoter sequences. STAT3 expression in particular has been associated with Abl, Src, and HTLV-1 transformation of normal cells. B-1 lymphocytes are self-renewing, CD5+ B cells that display a propensity for malignant transformation and are the normal counterpart to human chronic lymphocytic leukemias. Further, B-1 cells are characterized by aberrant intracellular signaling, including hyperresponsiveness to phorbol ester PKC agonists. Here we demonstrate that B-1 lymphocytes constitutively express nuclear activated STAT3, which is not expressed by unmanipulated conventional (B-2) lymphocytes. In contrast, STAT3 activation is induced in B-2 cells after antigen receptor engagement in a delayed fashion (after 3 h). Induction of STAT3 is inhibited by both the serine/threonine protein kinase inhibitor H-7 and the immunosuppressive drug rapamycin and requires de novo protein synthesis, demonstrating novel coupling between sIg and STAT proteins that differs from the classical paradigm for STAT induction by cytokine receptors. The inability of prolonged stimulation of conventional B-2 cells with anti-Ig, a treatment sufficient to induce CD5 expression, to result in sustained STAT3 activation suggests that STAT3 is a specific nuclear marker for B-1 cells. Thus, STAT3 may play a role in B cell antigen-specific signaling responses, and its constitutive activation is associated with a normal cell population exhibiting intrinsic proliferative behavior.

Are antibodies important in mice infected with Plasmodium yoelii?

It is unwise to extrapolate results, even from one mouse strain to another, when attempting to define the mechanisms that control and effect anti-malaria immunity. It is important to better characterize the broad range o f possible responses that are likely to occur when individuals in an outbred population are infected. Here, Peter Sayles and Donald Wossom discuss briefly their views on the role of antibody in murine and human malaria infections, based on their work on mice infected with Plasmodium yoelii.

Molecular analysis of immunoglobulin heavy chain genes coding for idiotypic and anti-idiotypic antibodies involved in B-B cellular interaction

We recently reported that a unique B cell clone (B19-1d), specific for a cross-reactive idiotype (CRI) on MOPC104E myeloma protein (M104E), enhances Igh-restricted CRI+ antibody production. In this paper, we report the nucleotide sequences of immunoglobulin heavy chain variable regions (VH) of both M104E and B19-1d-derived hybridoma (HB19) antibodies. The sequence data revealed that both belong to the J558 germ line VH gene subfamily. Strikingly, not only the VH region, but also the leader sequences of M104E and HB19 are very similar to each other at 88% (VH) and 91% (leader) homology, but they use different D and J segments. The VH region sequence similarity is highest among the germ line VH gene sequences of the BALB/c J558 subfamily so far screened. Southern hybridization data, using 5'-noncoding regions of either M104E or HB19 genomic VH gene clones as probes, revealed that both VH genes are conserved in the M104E CRI producer strains of mice. Moreover, these probes show the restriction length polymorphism pattern of mouse VH genes in various strains. That the HB19 VH gene locates to the 5' upper arm of the M104E VH gene on the chromosome was suggested by Southern blot hybridization. Immunoglobulin VH gene restriction of idiotypic and antiidiotypic B-B cellular interaction is discussed from a molecular point of view.

Human anti-pneumococcal polysaccharide antibodies are secreted by the CD5- B cell lineage

To determine whether human antibody responses to T cell-independent pneumococcal polysaccharide antigens are derived from CD5+ or CD5- B cells, we utilized an ELISPOT assay to detect individual anti-polysaccharide antibody-secreting cells. Human anti-type IV pneumococcal polysaccharide antibody-secreting cells were found in the CD5- B cell subpopulation. An EBV transformed anti-pneumococcal antibody-secreting B cell line was also CD5-. The ontogeny of CD5 expressing B cells correlated with the age at which polysaccharide responsiveness is acquired (generally around age 2 years in humans). The CD5- B cell subset represents only 25-30% of the B cells in young children, but this fraction increases throughout childhood to a plateau of 70-80% of the B cells in adults. These results support the hypothesis that the developmental change in responsiveness to T cell-independent polysaccharide antigens in humans is associated with maturation of the CD5- B cell subset.

Regulatory aspects of clonally expanded B-1 (CD5+ B) cells

B-1 (CD5+ B) cells appear early in ontogeny, produce mainly unmutated polyreactive antibodies, and are capable of self-renewal. B-1 cells clonally expand with age and are the malignant cell in chronic lymphocytic leukemia. In this report immunological analysis of B-1 malignancies in NZB mice, a murine model of chronic lymphocytic leukemia, is related to current information on B-1 cells. B-1 clones from NZB mice produce high levels of interleukin-10, detected at the RNA level by semi-quantitative polymerase chain reaction. In addition, the B-1 malignant clones in NZB mice and their hybrids, are negative for B220/6B2 expression, the B-specific antigenic form of CD45 which is a membrane-associated phosphatase involved in lymphocyte activation. Both the autocrine production by B-1 cells of interleukin-10 and altered CD45 expression may be responsible for the clonal expansion of these cells, as well as the accompanying T cell expansion. We report the establishment of an in vitro cytotoxic CD8+ T cell line derived from an NZB with a B-1 malignancy. The effect of B-1 cell-derived interleukin-10 on subsets of T lymphocytes may account for the immunoregulatory properties of B-1 cells. In addition, the NZB malignancies were also characterized for immunoglobulin variable region sequence and antigen specificity. The B-1 malignancies produced immunoglobulin derived from unmutated germline sequences with no N base substitutions. It appears that both the immunoglobulin and interleukin-10 produced by the B-1 malignant cell in NZB mice may have immunoregulatory properties. A study of B-1 malignancies may shed light on the immunoregulatory properties of non-clonally expanded normal B-1 cells.

Surface markers, heavy chain sequences and B cell lineages

A unifying theory of B cell development and lineage commitment is presented. There are two firmly established B lineages: cells which normally arise only from fetal sources and lack N insertions in their rearranged heavy chains; and N-containing cells which arise from adult bone marrow precursors (and perhaps from late fetal sources). Commitment to the expression of CD5 and the capacity for long-life (or self-renewal) are induced as a consequence of sIg cross-linking, typically by a repeating epitope, thymus independent type two antigen. Alternatively, activation resulting from cognate interaction with a helper T cell does not induce CD5 but results in lower expression of J11d. In this case activation occurs in the absence of sIg cross-linking. It is further proposed that differences in the Ig repertoire make it highly likely that fetal/neonatal, but not adult derived B cells will be induced to express CD5. The model offers a plausible explanation for the correlation of CD5 expression and natural autoantibody production by neonatal B cells. Possible sources of pathogenic autoantibody are discussed in the context of this model.

The role of antibodies in the regulation of delayed-type hypersensitivity

The contribution of B cells and antibodies to the regulation of delayed-type hypersensitivity (DTH) was investigated in mice rendered B-cell-deficient by treatment with anti-mu antibodies. In normal rabbit immunoglobulin (Ig)-treated mice as well as normal mice, the intravenous injection of a large amount of keyhole limpet haemocyanin (KLH) suppressed DTH, and serum titres of the anti-KLH antibody were significantly elevated. However, in anti-mu-treated mice, the intravenous injection of a large amount of KLH could not induce either suppression of DTH or the elevation of anti-KLH antibody titres. The transfer of anti-KLH antibodies suppressed DTH in a H-2 non-restricted, probably Igh-restricted, way in anti-mu-treated mice. In addition, the transfer of anti-KLH antibodies induced effector-phase suppressor T cells whose phenotype was L3T4-, Lyt-2+. We concluded that antibodies play a significant role in the regulation of DTH.

Ontogeny of thymic B cells in normal mice

Ontogeny of thymic B cells and their surface characteristics were analyzed using monoclonal antibodies (mAbs) against B220 molecules (CD45, CD45R). A small number of B cells were detected in fetal thymus on Gestation Day 14 (approximately 3.5% of the low-density fraction). Similarly, the percentage of B cells in the low-density fraction was 3.2% on Gestation Day 18, and 3.5% on Day 1 after birth. These were the same level as that of adult mice. CD5+ B cells, which form the major population of thymic B cells, were also found in the fetal life (0.5% on Day 14 and 2.2% on Day 16 in the low-density cells). The percentage of CD5+ B cells in B cell-enriched fraction was about 65% on Day 1 after birth, which is the same level as that in adult mice. These results indicate that a small number of B cells or cells in the B-cell lineage are present in the fetal thymus and also suggest the importance of these thymic B cells in the negative selection of T cells during early developmental stages.

B-cell-mediated regulation of delayed-type hypersensitivity

We obtained immune sera from mice which received suppressor B cells induced in vitro, injected them into immunized mice, and measured suppression of the delayed-type hypersensitivity (DTH) of these recipient mice. In the recipients, effector-phase suppressor T (Ts) cells were induced, and the action of these Ts cells was antigen-nonspecific. The suppressive material of the sera was adsorbed on a Sepharose column coated with anti-mouse immunoglobulin antibody and acid elution of the column yielded the elute fraction that showed significant suppressive activity. The suppressive activity of the sera was also adsorbed by an antigen-coated Sepharose column, and the eluate from the column had suppressive activity. Moreover, we established antigen-specific monoclonal antibodies, some of which suppressed the DTH in an H-2-nonrestricted way. The isotype or specificity of the antibodies was not related to the suppression, because suppressive and nonsuppressive antibodies belonged to the same immunoglobulin isotype and because the antibodies that recognized the same epitope had different suppressive activities. The Fc portion was not the functional site, because the F(ab')2 fragment had the activity. The suppressive antibody induced effector-phase Ts cells, which had the anti-idiotypic receptor. These findings suggested that antigen-specific antibodies in the immune sera mediated the suppression of DTH by the induction of effector-phase Ts cells in vivo and the idiotype of the antibody stimulated the anti-idiotypic receptor of these Ts cells.

Possible immunoregulatory role for CD5 + B cells

CD5 + B cells represent a subpopulation of B cells which have the characteristic of employing unmutated immunoglobulin variable region genes. These cells are found to be increased early in ontogeny. The percentage of CD5 + B cells is highest in the fetus and decreases after birth. The antibodies produced by CD5 + B cells are polyreactive and are the natural autoantibodies. These autoantibodies may not be pathogenic. CD5 + B cells are elevated in certain autoimmune disease states and are the malignant cell type in B-CLL, with a strong genetic component involved in determining elevated CD5 + B cell states. Elevated CD5 + B cells are found in immunodeficient states (young, aged, and autoimmune). CD5 + B cells may normally act as a first-line defense against invading foreign pathogens but are not involved in the specific immune response. There is some evidence, at least in newborns, that CD5 + B cells may affect the emerging B cell repertoire of conventional B cells via idiotype cascade. However, the action of CD5 + B cells in the newborn may be quite different than their activity in the adult. Nonimmunoglobulin-producing CD5 + B cells may be immunosuppressors. In this report, a unique subpopulation of CD5 + B cells was investigated. These cells were found only in the spleens of aged NZB mice. The CD5 + B cells were clonal and possessed extra chromosomes and did not appear to be producing antibodies. These cells were capable of rapid proliferation in unirradiated recipients. By taking advantage of this proliferative capability, the effect of exogenous clonal CD5 + B cells on recipient immune system was evaluated. Clonal CD5 + B cells from NZB mice were immunosuppressive and decreased the numbers of conventional B cells as well as the level of "natural antibodies." In summary, CD5 + B cells may play different roles in the immune system depending upon environment, age, and their differentiation state (i.e., proliferation versus antibody secretion). The natural antibody produced by CD5 + B cells may be involved in maintenance functions such as removal of dead cells and first-line defense mechanisms. In addition, CD5 + B cells may themselves regulate the immune system and produce a factor which is immunosuppressive. An understanding of the various functions of CD5 + B cells may elucidate fundamental immunoregulatory circuits.

Elevated expression of Pgp-1 (Ly-24) by murine peritoneal B lymphocytes

B cell expression of the surface glycoprotein, Pgp-1 (Ly-24), was evaluated using flow cytometric analysis. Pgp-1 expression on naive, conventional (splenic) B cells was low but could be increased by mitogenic stimulation. Pgp-1 expression on naive peritoneal B cells was higher than expression by unmanipulated conventional B cells, suggesting the possibility that peritoneal B cells have been activated in vivo. However, the elevated expression of Pgp-1 by peritoneal B cells was not accompanied by increased expression of surface Ia but was correlated with Ly-1 status. Further, Pgp-1 expression by B cells from germ-free mice did not differ from that of normal animals. The elevated expression of Pgp-1 by peritoneal B cells is superficially similar to that provoked by mitogenic stimulation of conventional B cells; however, several characteristics suggest that the elevated expression of Pgp-1 by peritoneal B cells does not reflect prior activation of these cells.

Characterization of the immunodeficiency of RIIIS/J mice: immune response to polysaccharide antigens

RIIIS/J mice lack an autosomal dominant gene(s) that influences the magnitude of the antibody response to several polysaccharide antigens of bacterial origin. Low responsiveness is demonstrable whether polysaccharide is administered as a T-helper-cell-independent or -dependent antigen conjugated to an immunogenic carrier; however, RIIIS/J mice make good anti-hapten antibody responses to haptenated polysaccharides. The low antibody responses of RIIIS/J mice to type III pneumococcal polysaccharide do not appear to be the results of an imbalance in the activity of regulatory T lymphocytes. Compared with other strains of mice, RIIIS/J mice elicit low antibody responses to lipopolysaccharide (LPS). They do not develop a cyclic primary or secondary antibody response to Escherichia coli O113 LPS; the latter is not due to a lack of mitogenic response to E. coli O113 LPS. They also produce auto-anti-idiotypic antibody after being immunized with trinitrophenyl-Ficoll.

Characterization of a B cell helper factor(s) derived from CD5+ B cell hybridomas

Work from our laboratory suggests that the selective advantage of frequently autoreactive CD5+ B cells is to provide activation signals to CD5- antigen-specific B cells. This hypothesis is supported by the observation that supernatants from CD5+ B cell hybridomas replace CD5+ B cell populations in helping idiotypic B cell subsets respond to antigen plus anti-idiotype antibody. The present study was designed to initiate the characterization of CD5+ B hybridoma-derived helper factor(s) (BHF) and to compare BHF to previously described cytokines. Elution of BHF from a lectin column enabled significant enrichment of the apparently glycosylated helper factor(s) from serum-free hybridoma supernatant. Gel filtration of this enriched activity revealed two significant peaks of helper activity, one at approximately 19-22 kDa and a second at 29-32 kDa. BHF activity in each fraction was sensitive to protease treatment. To determine if some previously described cytokines of approximately the same molecular weights were responsible for BHF activity, BHF fractions were tested for cytokine activity in respective bioassays. At least 2000 units of BHF did not contain detectable levels of IL-1, IL-2, IL-3, IL-4, IL-6, GM-CSF, G-CSF, or IFN-gamma activity. Furthermore, three hybridomas which produced BHF did not transcribe detectable levels of mRNAs specific for IL-1, IL-2, IL-3, IL-4, IL-5, IL-6, GM-CSF, or IFN-gamma. The results suggest that CD5+ B cell hybridomas produce a lymphokine(s) distinct from cytokines commonly associated with B cell activation. The potential roles of this lymphokine in immunity and disease are discussed.

CD5-positive B-cell malignancies frequently express cross-reactive idiotypes associated with IgM autoantibodies

Using monoclonal antibodies (MAb) specific for cross-reactive idiotypes (CRIs) associated with human monoclonal IgM autoantibodies, we examined 57 biopsy specimens that previously had been noted to have immunohistologic features of CD5-positive B-cell small lymphocytic (SL) non-Hodgkin's lymphoma (NHL). Twenty-five lymphoma specimens were noted to be from patients with chronic lymphocytic leukemia (CLL). Eight of thirty-four (24%) immunoglobulin (Ig) kappa light-chain expressing lymphomas reacted with 17.109, a MAb specific for a major CRI encoded by a conserved Ig kappa variable region gene (Vk gene) of the VkIIIb sub-subgroup. All 17.109-reactive tissues and two 17.109-negative specimens were recognized by another MAb specific for VkIIIb framework determinant(s). Seven of all fifty-six (13%) Ig-expressing tumors bound G6, a MAb specific for an autoantibody heavy-chain-associated CRI that is encoded by a conserved antibody heavy chain variable region gene(s) (VHgene) of the VH1 subgroup. All seven G6-positive lymphomas and two G6-negative tumors reacted with Cc1, another MAb specific for a rheumatoid factor heavy-chain-associated CRI. A third autoantibody-heavy-chain-associated CRI, termed Lc1, was expressed by seven (13%) other lymphomas. Finally, a fourth MAb specific for RF heavy-chain-associated CRI, named B6, detected two additional tumors. The expression frequencies of autoantibody-associated CRIs among SL NHL patients without peripheral lymphocytosis did not differ from those noted among patients with CLL but were significantly higher than those observed among patients with NHL of follicular center-cell origin. These data imply that the malignant B cells of patients with either CD5-positive B-cell SL NHL or CLL express a restricted set of Ig V genes that have not substantially diversified from the germline DNA.

The relationship between CD5-expressing B lymphocytes and serologic abnormalities in rheumatoid arthritis patients and their relatives

The influence of genetic factors on the expression of CD5+ B lymphocytes and their relationship to a broad spectrum of autoantibodies was investigated in a study of 12 patients with rheumatoid arthritis (RA) and 52 of their healthy first-degree relatives. The proportion of CD5+ B cells was significantly higher in RA patients (mean +/- SEM 23.9 +/- 2.7%) compared with that in their relatives (18.3 +/- 1.1%, P less than 0.05) and compared with that in a group of healthy control subjects (16.1 +/- 1.8%; P less than 0.05). Much more striking, however, were the high levels of CD5+ B cells found in the patients and their relatives in 5 of the families studied. Increases in total immunoglobulin levels and autoantibody levels were frequently observed in RA patients (approximately 20-40%) and their relatives (approximately 10-20%). Furthermore, a statistically significant correlation (P less than 0.01) between IgM rheumatoid factor and the percentage of B lymphocytes expressing CD5 was observed.

Unusual phenotype of B cells in the thymus of normal mice

A small number of B cells are found in the thymus of normal mice. A population of B lymphocytes could be enriched to greater than 90% purity by isolating a low-density fraction on Percoll density gradients and then depleting T cells with a mixture of anti-Thy-1, CD4, and CD8 mAbs and complement. Enrichment was monitored by surface Ig staining and by functional studies (responsiveness to LPS, and to anti-mu plus IL-4). When the phenotype of these B cells was studied by flow cytometry, 60-80% had the phenotype Ly-1+ (CD5), Ia+, B220low (CD45R), and Mac-1+ (CD 11b). In contrast, splenic B cells lacked CD5 and CD11b and expressed higher levels of B220 and Ia antigens. These results indicate that most thymic B cells have the phenotype of the Ly-1 B cell subset, which was identified previously as a trace subpopulation in some peripheral tissues and is thought to play a role in autoantibody formation.

Down-regulation of suppressor cell induction

A unidirectional cascade of cell interactions has been described previously that involves at least three distinct populations of suppressor T cells (Ts) that interact in appropriate succession to mediate suppression of delayed hypersensitivity responses to the 4-hydroxy-3-nitrophenylacetyl hapten (NP). The present work focuses on the potential bidirectional effects of one suppressor factor and how it can regulate the homeostatic mechanisms that maintain this suppressor cell cascade. Specifically, the effects of prior administration of mice with a transducer suppressor factor (TsF2) on the generation of NP-specific TS1 suppressor cells were evaluated. It was observed that the TSF2 given 2-14 days prior to administration of the tolerogen (NP-coupled splenic-adherent cells) interfered with the development of inducer TS1 suppressor cells. This down-regulation of suppressor cell induction is mediated by a population of cells that have the following characteristics: NP-binding, Lyt-1+2-, L3T4+, I-J+, and Vicia villosa (VV)-adherent T cells (for convenience these cells are termed anti-suppressor cells). Furthermore, there are genetic restrictions (both H-2 and IgH) between TSF2 and host which control the generation of anti-suppressor cells. The results suggest that TSF2 may have a role in homeostatic mechanisms that regulate the NP-specific suppressor cell cascade. The relationship of anti-suppressor and contra-suppressor cells is discussed.

B cell participation in the recursive selection of T cell repertoires

Normal BALB/c mice produce 2,4,6-trinitrophenyl (TNP)-I-Ad specific T helper (Th) cells expressing a receptor heterodimer which share with anti-TNP antibodies an idiotope defined by the F6(51) anti-idiotypic antibody. Expression of this Th idiotype is controlled by major histocompatibility complex and immunoglobulin heavy chain-linked genes and results from antibody-dependent selection of T cell repertoires (Martinez-A. et al., Eur. J. Immunol. 1986. 16: 417). We now present evidence for the recursive nature of T----B cell repertoire selection and suggest that perinatal B cells, present in adult peritoneal cavity, operate in the early phases of this process. Thus, the Th idiotype is absent in BALB/c mice which are either suppressed from birth with anti-mu antibodies, or reconstituted with autologous bone marrow after lethal irradiation as adults. Supplementation of bone marrow reconstitution with syngeneic Thy-1-, Ly-1+ peritoneal B cells, however, selects Th cell repertoires that are undistinguishable from normal mice as to expression of the F6(51) clonotype. This effect is lost after depletion of Ly-1+ cells in the reconstituting Thy-1- peritoneal cell population. Interestingly, large in vivo "naturally" activated Ly-1- splenic B cells can also reconstitute Th idiotype expression if they are isolated from normal, but not from athymic, nude donors. However, transfer of normal large splenic T cells to adult nude mice "educates" the splenic "large B cell" compartment in these animals such that they acquire the ability to recursively select, upon transfer to bone marrow reconstituted recipients, the Th clonotype.(ABSTRACT TRUNCATED AT 250 WORDS)

Autoantibody-associated kappa light chain variable region gene expressed in chronic lymphocytic leukemia with little or no somatic mutation. Implications for etiology and immunotherapy

Recently the minor B cell subpopulation that expresses the CD5 (Leu-1) antigen has been implicated as a source of IgM autoantibodies. Chronic lymphocytic leukemia (CLL), the most common leukemia in humans, represents a malignancy of small B lymphocytes that also express the CD5 antigen. However, little is known concerning the antibody variable region genes (V genes) that are used by these malignant CD5 B cells. We have found that a relatively high frequency of CLL patients have leukemic B cells with surface immunoglobulin (sIg) recognized by 17.109, a murine mAb specific for a kappa light chain associated crossreactive idiotype (CRI) associated with rheumatoid factor and other IgM autoantibodies. Flow cytometric analyses revealed that the relative expression of the 17.109-CRI by circulating leukemic B cells was directly proportional to the levels of sIg kappa light chain, indicating that there exists stable idiotype expression in the leukemic population. To examine this at the molecular level, the nucleic acid sequences encoding the Ig kappa light chains of two unrelated patients with CLL bearing sIg with the 17.109-CRI were determined. Analyses of multiple independent kappa light chain cDNA clones did not reveal any evidence for sequence heterogeneity in the CLL cell population. Furthermore, the nucleic acid sequences expressed by the leukemic cells of these two patients were identical or very homologous to a germline V kappa gene isolated from placental DNA, designated Humkv 325, or "V kappa RF" because of its association with IgM autoantibodies. This study suggests; (a) that the malignant CD5+ B lymphocytes in CLL use the same V kappa gene that has been highly associated with IgM autoantibodies and (b) that the expression of V genes is stable in CLL, in contrast to other B cell malignancies examined to date. We propose that many CLL cases represent malignancies of autoreactive CD5 B cells that use a restricted set of conserved V genes. This property may render CLL particularly amenable to immunotherapy with antiidiotypic antibodies.

Characterization of proximal colonic lymphoid tissue in the mouse

Here we describe a nodule of lymphoid tissue which was consistently located in the proximal colon of mice approximately 25% of the distance from the cecum to the rectum. Immunohistochemical characterization of this nodule demonstrated that the majority of lymphocytes were relatively immature 14.8+ (B220+), IgM+, Ia+ (specificity 20) B cells some of which were also Ly-1+. These nodules also possessed an occasional T cell (Thy-1+, Ly-1+, Lyt-2+) aggregate at the periphery. Rare, small areas did not stain for either T or B cell markers. These lymphoid nodules were associated with epithelial cells which stained positively with the ER-TR4 monoclonal antibody (which also recognizes thymic cortical epithelial cells) and also with ER-TR6, which has been reported to recognize thymic macrophages or dendritic cells. The overlying colonic epithelium stained intensely with the ER-TR4 monoclonal antibody. Proximal colonic lymphoid tissue was extremely sensitive to steroid treatment, losing approximately 80% of its mass within 24 hours in response to a single intraperitoneal injection of 2 mg hydrocortisone acetate. This response was similar to that of the thymus and to that reported for the bursa of Fabricius, but unlike that of other gastrointestinal lymphoid aggregates. These results indicated that proximal colonic lymphoid tissue contains a high frequency of relatively immature B cells and may be a primary site of their generation, possibly including some of the Ly-1+ phenotype. These observations correlate with new evidence suggesting that the allantois participates in the formation of the distal midgut, including its lymphoid components.

Analysis of murine lymphocyte subpopulations by dual-color flow cytometry: technical considerations and specificities of monoclonal antibodies directed against surface markers

We performed detailed phenotypic analysis of murine lymphocytes from thymus, spleen, lymph node, and peripheral blood using commercially available monoclonal antibodies, each with specificities for membrane surface markers and dual-color flow cytometry. Erythrocyte lysis techniques were utilized for lymphocyte preparation so that inherent difficulties with gradient techniques would be avoided, such as the potential for loss of abnormally sized cells. These studies demonstrated that the specificities of each monoclonal must be carefully determined; for example, the Lyt-1 monoclonal, frequently utilized to identify helper/inducer T cells, also reacts with suppressor/cytotoxic (Lyt-2+) cells; helper/inducer cells are better studied with a more recently available monoclonal, L3T4. Cells from different tissues may differ greatly not only in the presence of surface markers, but also in the surface density of each marker; this density can be studied and quantitated using appropriate analytic software. We also show that larger and more granular lymphocytes appear to be enriched for surface Ia antigen, indicating that these cells may be activated or regulatory subsets; these large, Ia+ T-cells will be lost from analysis if standard, narrow gate settings are used for analyzing forward and side-scatter characteristics or for cell sorting.

The CD5+ B cell: a B cell lineage with a central role in autoimmune disease?

It is apparent that B cells are heterogeneous with respect to, for example, the antigens they express on their surface, and the stimuli to which they can respond. It is still unclear to what extent these differences relate to the stage of differentiation (eg. virgin B cells differing from activated B cells or memory cells), or whether distinct developmental lineages might exist. It has been proposed by some authors that, in the mouse, B cells expressing the ly-1 antigen constitute a separate lineage. In man also, a minor population of B cells expresses detectable levels of the CD5 antigen, but far less information is available about these cells. Interest in the CD5+ and ly-1+ B cell subpopulations has been further stimulated by the suggestion that these cells might play a special role in autoimmune disease. Although, in mouse, ly-1+ B cells differ in several respects from ly-1- B cells, the main evidence that they form a separate lineage derives from experiments in which ly-1+ B cells could not be reconstituted with adult bone marrow. It should be borne in mind that the situation is quite different in humans where, following bone marrow transplantation, CD5+ B cells are rapidly restored. Moreover, in the irradiated mice, at least in some of the experiments ly-1+ B cells were in fact reconstituted by adult bone marrow. Furthermore, at least in humans, expression of CD5 can sometimes be induced. There is, as yet, no good evidence that human CD5+ B cells form a distinct lineage, and it is possible that CD5 expression depends upon microenvironmental influences acting on the B cell during its differentiation. Several interesting properties have been attributed to ly-1+ B cells, including the ability to provide help to other B cells, and the secretion of autocrine factors. However there is also evidence that these features are not exclusive to B cells expressing ly-1. It has also been suggested that ly-1+ B cells might be long-lived. It is not yet known whether some of the properties of ly-1+ B cells might be a direct result of their expressing this antigen; this may become more clear when the function of CD5 is elucidated. The suggestion that the repertoire of ly-1+ B cells might be biased towards the expression of certain V genes is very interesting. Many of the hybridomas from neonatal mice produce antibodies which are multi-specific, and therefore well suited to form a first line of defence against potential pathogens.(ABSTRACT TRUNCATED AT 400 WORDS)

Non-phagocytic adherent cells as contaminants in peritoneal macrophage cultures from conventionally housed mice

Non-phagocytic adherent cells (NPAC) were found as contaminants in peritoneal macrophage cultures from mice kept in conventional animal houses. The cells were morphologically intermediates between macrophages and small lymphocytes. They showed a vigorous ameboid movement in vitro, and most of the cells detached during the first 24 h in culture. The cells were identified as B-lymphocytes by demonstrating surface immunoglobulin with fluorescence labelled goat-F(ab)2-anti-mouse IgG + IgM antibody, as non-phagocytes by latex beads phagocytosis test, and as non-T cells with an anti-Thy 1 monoclonal antibody. Macrophages were identified with M1/70 monoclonal antibody against the Mac-1 antigen. An increased number of NPAC was found in cultures harvested from the peritoneum of mice kept in conventional houses for one week or more, together with a rise in total peritoneal cell count. The keeping also resulted in increased functional activity of the macrophages, tested by morphology, lososomal enzyme activity and phagocytic functions. The rise in NPAC parallelled the activation of macrophages and may therefore serve as an indication of the functional state of the macrophage cultures.

Evolutionary and somatic selection of the antibody repertoire in the mouse

The repertoire of antibody variable (V) regions has been subject to evolutionary selection, affecting both the diversity of V region genes in the germline and their expression in the B lymphocyte population and its subsets. In ontogeny, contact with an antigen leads to the expansion of B cells expressing antibodies complementary to it. In a defined phase of B cell differentiation, new sets of V regions are generated from the existing repertoire through somatic hypermutation. Cells carrying advantageous antibody mutants are selected into the memory compartment and produce a stable secondary response upon reexposure to the antigen.

The Leu-1 B-cell subpopulation in patients with rheumatoid arthritis

Ly-1-B cells have been shown to be elevated in autoimmune mice, especially NZB, and to secrete IgM autoantibody, suggesting that Ly-1 B cells may participate in autoimmune diseases. In this study, B-cell populations carrying Leu-1, a human T-cell surface molecule homologous to mouse Ly-1 (Leu-1 B), were examined by dual fluorescence flow cytometry, in peripheral blood lymphocytes taken from patients suffering from various autoimmune disease. These B cells were shown to be present at a significantly high percentage in rheumatoid arthritis (RA) patients. There was no significant correlation among the incidence of Leu-1 B cells, rheumatoid factor (RF) titers, and the amount of IgM production in vitro. There was, however, a significantly high incidence of Leu-1 B cells in RA patients with a high RF titer (greater than 5 X 2(13), suggesting that these B cells in RA may play an important role in IgM RF production in vivo.

Intermediate lymphocytic lymphoma: an immunohistologic study with comparison to other lymphocytic lymphomas

In an immunohistologic analysis of 13 cases of intermediate lymphocytic lymphoma (ILL), the immunophenotype of ILL was compared to the immunophenotypes of other B-lymphocytic lymphomas and the normal lymphoid follicle to determine the normal cell in the scheme of B-cell differentiation that corresponds to ILL. The characteristic immunophenotype of ILL was surface IgM +/- D+, cytoplasmic immunoglobulin -, B1+, BA1+, B2-, BA2-, B4+, Leu 14+, HLA-DR+, Leu 1+, and common acute lymphoblastic leukemia associated (CALLA) antigen -. The immunophenotype of ILL was similar to that of lymphocytes in normal primary follicles and the mantle zones of secondary follicles. The "immature" phenotype of ILL was identical to that of small lymphocytic lymphoma, which strongly supports their close lineage relationship. In contrast, the "mature" phenotypes of the follicular center cell and lymphoplasmacytoid lymphomas suggest that they correspond to normal cells at later stages of differentiation. Our findings indicate that B-lymphocytic lymphomas recapitulate the normal stages of B-cell differentiation. The cell of ILL appears to be an immature B cell that homes to, and resides in, primary follicles and the mantle zones of secondary follicles. The cytologic, architectural, immunologic, and clinical features of ILL indicate that it should be included as a separate category in the International Working Formulation.

B lymphocyte reconstitution after human bone marrow transplantation. Leu-1 antigen defines a distinct population of B lymphocytes

Differences in the expression of Leu-1 (CD5) define two populations of recovering B cells after human marrow transplantation, Leu-1+ and Leu-1- B cells. The Leu-1+ B cells were polyclonal, of donor origin, and did not express detectable interleukin 2 receptor. Leu-1+ B cells generally appeared 2-4 wk after marrow grafting and often preceded the recovery of Leu-1- B cells. Acute and chronic graft vs. host disease (GvHD) resulted in the recovery of significantly fewer Leu-1+ B cells, whereas Leu-1- B cells were only decreased in acute GvHD. Multivariate analysis showed no significant effect of age, disease, prednisone or azathioprine, or ex vivo treatment of the marrow with anti-Leu-1 and complement on recovery of Leu-1+ and Leu-1- B cells, independent of the effects of GvHD. Leu-1+ B cells are a major lymphocyte population posttransplant. They may reflect a stage of differentiation of normal B cells or a separate B cell lineage.

Long-term-cultured mouse B-lymphocyte line. I. Establishment and characterization of mouse B-lymphocyte line

Mouse B-cell line was established by culturing anti-Thy-1 antibody and complement-treated splenic B cells with the conditioned medium of concanavalin A-stimulated spleen cell-culture supernatant. At the eighth week of culture, it was revealed that 100% of the long-term-cultured cells had both cytoplasmic and surface immunoglobulin. These cells were then maintained in the conditioned medium together with T-cell-depleted splenic and then splenic adherent feeder cells. Flow cytometric studies of the B-cell line showed that they had surface mu, delta, and kappa but no gamma, lambda, Lyt-1, or Lyt-2. The growth of the B-cell line was dependent on the factor(s) derived from concanavalin A-stimulated conditioned medium. It was found that IL-2 was the major factor supporting the B-cell growth. The B-cell line did not secrete immunoglobulin spontaneously, but it could differentiate into antibody-forming cells through the stimulation of bacterial lipopolysaccharides. The technique for obtaining mouse B-cell lines are reproducible in our laboratory and one of those lines has been propagated and maintained for 16 months to the present.

B-Ly1 cells: immortal Ly-1+ B lymphocyte cell lines spontaneously arising in murine splenic cultures

We have surveyed the molecular and functional properties of B-Ly1 cells, spontaneously occurring Ly-1+ cell tissue cultures lines established from murine spleen. Several features are surprising when compared to the conventional understanding of B cell physiology: In contrast to the major B cell subpopulation, these cells establish stable in vitro lines in the absence of nominal growth factors. This outgrowth is consistently accompanied by c-myc amplification and deregulation, and resistance to the effects of an autoregulatory IgM species which normally curtails the growth of B cells. These properties may be relevant to the disproportionate occurrence of Ly-1+ B cell malignancies in vivo. B-Ly1 cell lines consistently delete immunoglobulin constant region genes, and uniformly express lambda light chains, a rare murine isotype. These features may be causally related, and may reflect a novel recombinational activity (see this volume). Immunoglobulin expression can be modulated by conventional stimuli. However, the response is transient, and includes production of mature heavy chain isotypes ("class switching") without apparent switch deletion. Moreover, unstimulated B-Ly1 cells show transcriptional activity throughout the heavy chain locus, and a novel hypermutation activity affecting the immunoglobulin variable region. The mechanisms underlying this surprising pattern of immunoglobulin expression are unknown. However, one wonders whether this expression pattern, if common to Ly-1+ B cell in vivo, might provide modes to escape idiotypic or isotypic immunoregulation. If so, this may be relevant to the prevalence of autoantibody production by this subpopulation. Thus, we are hopeful that some of these unique properties, if confirmed in the Ly-1+ B cells in vivo, will provide more definitive markers for this subpopulation, and disclose mechanisms accounting for their distinctive physiology and pathophysiology.

Production of immunoglobulin isotypes by Ly-1+ B cells in viable motheaten and normal mice

Almost all B cells in autoimmune mice with the viable motheaten (mev) mutation express the Ly-1 cell surface antigen, which marks a minor population of B cells constituting a separate lineage in normal mice. Immunoglobulins primarily of the M and G3 classes, which in both normal and mev mice contain high levels of lambda light chain, are produced in excess in mev mice. These and other observations suggest that the development of B cells that express Ly-1 is regulated independently from the development of B cells that do not express Ly-1. B cells bearing the Ly-1 surface antigen may play specialized roles in the normal immune system and in autoimmunity by regulating other B cells via lymphokines, by producing antibodies to self and certain foreign antigens, and by preferentially secreting immunoglobulin M and immunoglobulin G3.

Secretory leukemic B cells express T cell markers in vitro. A phenomenon suppressed by TPA

Immunological and biochemical markers of leukemia/lymphoma cells have provided valuable insight into hematopoietic malignancy and normal differentiation. The general assumption is that as early lymphoid cells become committed towards terminal differentiation they lose their capacity for bimodal differentiation and cells become restricted to B or T cell development and function. We have observed that phenotypically "late" leukemic B cells close to secretory stage can spontaneously express mature T cell antigens (T11, T4 and T8) after culture in vitro. In further studies of these cells, it was found that the biochemical marker lactate Dehydrogenase (LD) follows the intermediate pattern expressed by thymocytes rather than that of typical B cells. The expression of T cell antigens can be blocked by incubating these cells with the phorbol ester TPA (12-0-tetradecanoyl phorbol 13 acetate) which promotes unidirectional B cell maturation to plasmacytoid cells in a way that mimics normal B cell differentiation. These observations indicate that presecretory malignant B cells are still programmed to express T cell biochemical and antigenic markers and this expression can be influenced by environmental conditions in vitro.

A rheumatoid arthritis B cell subset expresses a phenotype similar to that in chronic lymphocytic leukemia

An abnormal subpopulation of B cells expressing the T1 antigen, which is normally restricted to T cells, was demonstrated in the peripheral blood of 16 patients with rheumatoid arthritis. This T1+ B cell population accounted for a mean of 19.6% (upper limit 48%) of the circulating B cells and did not correlate with clinical disease activity, rheumatoid factor, or drug treatment. The highest percentage of T1+ B cells found in the blood of 8 patients with connective tissue diseases, including systemic lupus erythematosus, was 5% of the B cells, and for normal controls, it was was 3% of the B cells. As previously reported, we confirmed that the T1+,Ig+ phenotype was a feature of leukemic cells in B-type chronic lymphocytic leukemia. The finding of increased numbers of T1+ B cells in patients with rheumatoid arthritis and those with B-type chronic lymphocytic leukemia raises the possibility that these cells play a role in a spectrum of diseases, including those involving autoimmunity and malignancy.

Immunopathology of non-Hodgkin lymphomas

The immunopathological features of lymphocytic non-Hodgkin lymphomas (NHL), follicular centre cell tumours and "large-cell" NHL are described with particular emphasis on in situ evaluation of cryostat sections using monoclonal antibodies. The immunological phenotypes of tumour cells and the pattern of "reactive" cellular infiltrates with characteristic differences for the various subtypes are summarized. Immunological membrane features of the following lymphocytic NHL of B lymphocyte origin are discussed in detail: B-CLL (most common phenotype of the lymphoma cells: VIB-C5, To-15, Ia, Leu-1), lymphoplasmocytoid NHL (To-15, Ia), B-prolymphocytic leukaemia (VIB-C5, To15, Ia, Leu (+/-), FMC-7(+/-] and hairy-cell leukaemia (HCL: To-15, Ia, FMC-7). NHL of T-lymphocytes detailed in respect of mycosis fungoides and Sézary syndrome (OKT-3, OKT-4, OKT-11), to subtypes of T-CLL with particular emphasis on the "azurophilic" type, to T-zone NHL, and to adult T-cell leukaemia/lymphoma (OKT-3, OKT-4, OKT-11, anti-tac), all of them with the usual immunological phenotype of T-helper (TH) lymphocytes. NHL with a predominance of T-suppressor (TS) lymphocytes include the immunoblastic lymphadenopathy like T-cell lymphoma (OKT-3, OKT-8, OKT-11) and some lymphoepitheloid (Lennert) lymphomas. Immunological features of follicular centre cell tumours are discussed with emphasis on similarities and differences with the normal germinal centre. Tumour cells usually show the following membrane phenotype: centroblastic/centrocytic (cb/cc: To-15, VIL-Al, Ia; meshwork of non-neoplastic R4/23+, To-5 + DRC), centrocytic (VIB-C5, To-15, Leu-1, Ia; R4/23 and To-5 meshwork), centroblastic (cb, To-5, To-15, Ia, VIL-Al +/-). "Large-cell" NHL include the last entity (cb), immunoblastic (B-ib, T-ib) and lymphoblastic (lb) NHL and are discussed in respect to B-ib (Ia, To-15 +/-, VIL-Al +/-), T-lb (WT-1, OKT-6 +/-, OKT-11 +/-), pre-B-lb (VIB-C5, Ia, TdT, VIL-Al +/-) and Burkitt-type NHL (VIB-C5, VIL-Al, Ia, sIg). "Reactive" cellular infiltrates may account for a large fraction of the cellular content of NHL (e.g. the mean TH and TS content amount to about 40% of that seen in normal lymph nodes). In comparison to other NHL B-CLL and cb/cc showed the highest, HCL the lowest number of TH X TS exhibited less typical alterations.(ABSTRACT TRUNCATED AT 400 WORDS)