B-lymphocyte heterogeneity: ontogenetic development and organ distribution of B-lymphocyte populations defined by their density of surface immunoglobulin

Differential expression of CD22 (Lyb8) on murine B cells

Previous studies have established the distribution, biochemistry and functional attributes of human CD22, a B cell-restricted glycoprotein. Recently, molecular cloning of the murine CD22 equivalent revealed this molecule to be the same as the previously described Lyb8 alloantigen. Using the anti-Lyb8 mAb Cy34.1.2, the present report documents the expression patterns of CD22 within the murine B cell compartment. The results demonstrate that in the bone marrow, murine CD22 is absent on the surface of pro-B cells, pre-B cells and newly emerging IgM+ B cells. CD22 is present at a low density on immature IgMhi B cells and fully expressed on mature recirculating B cells. In the periphery, murine CD22 is expressed at mature levels on all B cell subsets including follicular, marginal zone, B1 and switched B cells. Further studies showed CD22 to be retained on activated murine B cells for extended periods. Finally, in combination with CD23 and heat stable antigen, CD22 can be used to delineate the immature splenic B cells, and distinguish them from follicular and marginal zone cells. Together, the results demonstrate murine CD22 to be a useful pan marker for all mature B cell subsets.

A simple method for negative and positive selection of murine and human IgM-bearing lymphocytes based on the use of antibody-coated silica microparticles

The use of octadecyl silica microparticles is proposed as an alternative method for negative and positive selection of IgM-bearing lymphocytes. SiC18 microparticles coated with affinity purified IgG anti-IgM were evaluated in their efficiency to deplete IgM-bearing cells. 6 mg of SiC18-IgG depleted an average of 97% IgM-bearing cells from a murine spleen cell suspension and of 84% IgM-bearing cells from human spleen cells. The viability of the selected cells was not affected by this procedure. We also analyzed the ability of whole serum to release IgM-bearing cells from the complex SiC18-target cell. The IgM releasing efficiency was 98%, with a resulting viability of 85%. These results indicate that SiC18 microparticles, saturated with specific antibodies, may be used as an alternative method for depletion or purification of cells bearing the corresponding antigen, from complex cell suspensions. The method is simple, efficient and inexpensive, representing an interesting alternative to the immunomagnetic selection.

VH gene family expression in mice with the xid defect

Preferential use of particular VH gene families in the response to specific antigens has been demonstrated in several systems. The lack of responses to certain types of antigens, therefore, could be the result of deletion of or failure to express some VH genes. Because CBA/N mice, which carry the X-linked immunodeficiency (xid) gene defect, have been shown to be unresponsive to thymus-independent polysaccharide antigens, it was of interest to examine if this unresponsiveness could be accounted for by abnormal expression of particular VH gene families. Using in situ hybridization on B cell colonies, we determined the expression of nine VH gene families in CBA/CaHN females (genotypically normal), CBA/N males (xid) and females (xid), and (CBA/N x CBA/CaHN)F1 males (xid) and females (phenotypically normal). Our results indicate that VH gene family expression, including the S107 family, in CBA/N males and F1 males, is similar to that of CBA/CaHN and F1 females with predominant expression of J558, the largest gene family, in all individuals. Interestingly, CBA/N female mice, which carry two defective X chromosomes, as a group expressed significantly reduced levels of the J558 gene family, and as individuals showed variation in which family was predominantly expressed. We conclude that the unresponsiveness of mice with the xid defect to polysaccharide antigens can not attributed to a failure to express the nine VH gene families that we examined. Our findings do not support previous studies (Primi, D., and P.-A. Cazenave 1986. J. Exp. Med. 165:357), which found an absence of expression of the S107 family in xid mice.

The rat B cell system: the anatomical localization of flow cytometry-defined B cell subpopulations

Two-color flow cytometrical (FCM) analysis of rat peripheral lymphoid organs shows two distinct IgM/IgD-defined B cell subpopulations, similar to those of the mouse: a major population of cells expressing little IgM and high levels of IgD (population I) and a minor population of cells expressing high levels of IgM but little IgD (population III). In peripheral lymphoid organs population III cells are mainly found in spleen where they represent about 25% of the B cells; population III cells are almost absent from lymph nodes and Peyer's patches. In adult bone marrow and in neonatal spleen the majority of IgM/IgD-defined B cells (greater than 70%) are population III cells, similar to what is observed in the mouse. In contrast with mice, only a low proportion of the cells (1%) recovered from the peritoneal cavity are B cells, and most of them belong to population I. Previously defined monoclonal antibodies (HIS22 and HIS24) to B cell forms of the leukocyte common antigen (CD45R) in combination with staining for surface IgM and surface IgD demonstrates a further heterogeneity of rat B cells by three-color FCM analyses. HIS22 labels most population I cells; population III cells and a small subset (about one third) of population I express only very low levels of the HIS22 determinant. HIS24 reacts with population I cells and subdivides population III into two subsets: about one third of splenic population III cells are brightly stained with this antibody whereas fluorescence of the remaining two-thirds is lower. The HIS24bright population III cells likely are newly formed B cells since cells with this phenotype are the predominant surface Ig population found in adult bone marrow and neonatal spleen. In tissue sections of lymphoid organs, HIS22- and HIS24-positive cells are mainly found in lymphoid follicles; splenic marginal zones are almost unstained. Combining immunohistological analysis with the FCM data, we therefore conclude that the small follicular B cells are in population I and marginal zone B cells are found in the HIS24dull population III. The in situ localization of HIS24bright population III cells and the HIS22dull population I cells is not clear.(ABSTRACT TRUNCATED AT 400 WORDS)

A phenotypic and functional analysis of long-lived B and T lymphocytes

The lymphocyte composition of spleen, lymph nodes, bone marrow, and thymus of mice submitted to hydroxyurea treatments for four consecutive days was studied. The treatment selects for small lymphocyte populations that represent between 4 and 20% of control numbers in the various organs. Spleen and bone marrow contain the same B cell population with a low IgM, high IgD, low I-E phenotype, which respond to LPS at control clonal frequencies. The T cell compartment is equally depleted, and the lymphocytes remaining contain frequencies of clonable cells in response to mitogens and IL-2 that are comparable to those detected in normal spleen cells. Overall, the results suggest that only a minor fraction of all lymphocytes in a normal young adult mouse have life spans longer than 4 days.

Enhancement of antibody responses by IgD-binding factors induced by anti-IgD treatment of spleen cells

Treatment of normal BALB/c splenocytes with anti-mouse IgD antibodies at 0 degrees C followed by incubation of the cells at 37 degrees C resulted in the formation of soluble factors that selectively inhibit rosette formation of lymphocytes bearing Fc delta receptors with IgD-coated erythrocytes (i.e., IgD-binding factors). Treatment of the same cells with anti-IgM antibodies failed to induce the formation of the factors. Analysis of cellular mechanisms indicated that polymerized surface IgD on B cells, as well as surface IgD-anti-IgD complexes shed from the B cells, induced T cells bearing Fc delta receptors to form IgD-binding factors. The factors formed by the anti-IgD treatment of splenic lymphocytes are composed of molecular mass species of 70 and 34 kDa, as estimated by gel filtration. Both the 70- and 34-kDa IgD-binding factors enhanced IgM and IgG1 plaque-forming cell responses of sheep erythrocyte-primed mouse spleen cells to the antigen.

Comparison of the clonal diversity of the B cell repertoires in adult mice that differ in the expression of cell surface IgD

To determine whether the expression of surface IgD (sIgD) influences the extent of the expressed B cell repertoire, the clonal diversity of the B cell population in mice treated chronically with anti-IgD (delta) antibodies has been compared with the B cell repertoire observed in control animals, using the splenic focus limiting dilution B cell assay. The results show that the phosphorylcholine (PC)-specific B cell precursor frequency in anti-delta antibody-treated mice is increased when compared with that of control mice. Isotype and idiotype (T15) analyses of PC clonal products from anti-delta antibody-treated and control mice revealed no distributional differences. Analyses of the 2,4-dinitrophenyl (DNP)- and fluoresein isothiocyanate-specific B cell repertoires confirmed that the equal or increased precursor frequencies observed in anti-delta antibody-treated mice are not specific for the PC antigen. The increased precursor frequency of B cells from anti-delta antibody-treated mice was not the result of increased homing of B cells from anti-delta antibody-treated mice to recipient spleens, since B cells from control mice homed twice as well to recipient spleens as did B cells from anti-delta antibody-treated mice. Other studies demonstrated that (a) on average, antibody-secreting clones were generated more slowly when B cells from anti-delta antibody-treated mice were used as a source of precursors than B cells of control mice and (b) both sIg- spleen cells and sIg+ spleen cells from anti-delta antibody-treated mice generated a higher frequency of specific antibody-secreting clones than did the corresponding populations from control mice. These observations suggest that a population of sIgM+sIgD- B cells exists that resembles sIgD+ B cells rather than neonatal or xid B cells in its ability to generate responses to PC and suggests that the sIgM+sIgD- B cells from anti-delta antibody-treated mice are more responsive than are sIgM+IgD+ B cells, regardless of antigenic specificity, to the stimuli provided in the splenic focus system. Finally, this study suggests that the expression of sIgD does not influence the extent of the expressed B cell repertoire.

Assessment of antigen-specific receptor function of surface immunoglobulin M and D with identical hapten specificity

Monoclonal B-cell lines expressing antigen-specific surface IgM or IgD were established by transferring the genes encoding immunoglobulin heavy (mu or delta) and light (kappa) chains specific for the hapten 2,4,6-trinitrophenyl (TNP) into a B-cell lymphoma line. Two IgMTNP and two IgDTNP transformants were selected on the basis of similar levels of anti-TNP idiotype expression by flow microfluorimetric analysis. The IgMTNP and IgDTNP transformants were compared in quantitative assays for their ability to bind TNP-carrier and present TNP-carrier to carrier-specific T cells. Our results indicate that IgMTNP and IgDTNP transformants have an equal capacity to bind and present specific antigen. Thus surface IgM and IgD, when present in equivalent amounts, function similarly as antigen receptors.

Development of B lymphocytes in mice heterozygous for the X-linked immunodeficiency (xid) mutation. xid inhibits development of all splenic and lymph node B cells at a stage subsequent to their initial formation in bone marrow

CBA/N mice were crossed with CBA/Ca-Pgk-1a to produce female F1 hybrids that were heterozygous for both xid and the phosphoglycerate kinase 1 (PGK-1) allozymes. PGK acted as a quantifiable marker for the frequency of cells in which the xid-bearing X chromosome was active in lymphocytic and other cell populations. In adults, such cells (termed xid cells) were virtually absent in FACS-sorted splenic and lymph node B cells, and in all three splenic subpopulations distinguished on the basis of their relative expression of membrane mu and delta chains. Thus, the xid mutation appeared to compromise the development of all B cells. Erythrocytes, thymocytes, T cells, and granulocytes were unaffected. Selection against xid cells was less pronounced in the spleens of 2-6-wk-old mice. In the bone marrow, there was evidence for selection against xid in the production of B cells (except at 2 wk of age), but not at the pre-B cell level. These data suggest that, in competition with normal non-xid cells, newly-formed xid B cells were less likely to be incorporated into the peripheral B cell pool.

Age-dependent isotype variation during secondary immune response in MRL/lpr mice producing autoanti-gamma-globulin antibodies

A profound inability to produce IgG anti-2,4,6-trinitrophenyl (TNP) antibodies during the secondary immune response elicited by a T-dependent antigen was observed in aged MLR/lpr mice. This unresponsiveness is associated with a significantly low indirect anti-TNP plaque-forming cell response and a weak in vitro anti-TNP response upon the culture of keyhole limpet hemocyanin-primed T cells and TNP-primed B cells in the presence of TNP. The markedly low IgG anti-TNP response observed in aged MLR/lpr mice cannot be related to the presence of rheumatoid factors which are observed during the secondary response, since MRL +/+ and 129/J mice, (non-autoimmune disease strains), also produce significant amounts of anti-gamma-globulin antibodies yet mount a strong IgG anti-TNP response.

Expression of an X-linked gene family (XLR) in late-stage B cells and its alteration by the xid mutation

One of the most extensively studied X-linked immunodeficiency disorder is the xid mutation of the mouse strain CBA/N. This mutation may involve a maturational defect as xid animals are unable to raise antibodies to soluble polysaccharide antigens, a function normally attributed to late-stage B cells. Moreover, studies using monoclonal antibodies have defined a B-cell surface antigen (BLA-2 or 14G8) that is expressed on most or all immature B lymphocytes, but not on a subpopulation of mature splenic B lymphocytes; this late-stage, 14G8 antigen-negative splenic B-cell subpopulation is apparently absent from mice bearing the xid defect. In the accompanying paper we describe the isolation of a cDNA clone recognizing a family of genes on the X chromosome, at least some of whose members are closely linked to the xid trait. We report here that this gene family, XLR, is transcribed in certain B- and T-cell lineage tumours, but not in macrophage tumours, or liver or kidney cells. We show that it is transcribed principally in late-stage, 14G8-negative B-cell tumours and plasmacytomas, but not in immature B-cell or pre-B-cell tumours. We are able to detect transcription in all of 12 plasmacytomas (secretory B-cell tumours) derived from mice with normal X chromosomes, but not in three plasmacytomas carrying the xid mutation. These data, combined with the restriction fragment length polymorphism analysis linking the XLR gene family to the xid mutation, suggests that the xid defect occurs within a member of this gene family.

The cellular IgE response of rodents to infection with Nippostrongylus brasiliensis, Trichinella spiralis and Schistosoma mansoni

The IgE response at the cellular level to helminthic infection was studied in BALB/c mice inoculated with the infective larvae of the nematodes Nippostrongylus brasiliensis (Nb) or Trichinella spiralis (Ts) or with the cercariae of the trematode Schistosoma mansoni (Sm). Changes in mesenteric lymph node (MLN) cell number, cell surface(s) IgD, IgM, IgE and Thy-1.2 and intracytoplasmic (c) IgE were recorded. In addition, a comparable study was conducted in rats infected with Nb. At 11 days after infection (DAI) of mice with Nb or Ts, or rats with Nb, there was a 3-fold increase in cell number in the MNL. There was a marked increase in cell number in the MLN of mice infected with Sm at 7 weeks after infection (WAI) and in the spleens of Sm-infected mice at 4 WAI. The percentage of cIgE+ cells increased from undetectable levels in uninfected mice and rats to as high as 0.5-1.3% in the MLN of helminth-infected mice and rats. Analysis of cell surface molecules with a fluorescence activated cell sorter (FACS) showed that Nb and Ts infection induced slight increases in the percentages of B cells and slight decreases in the percentage of T cells. More remarkably, the percentage of sIgE+ cells in the MLN of both Nb- and Ts-infected mice rose from undetectable levels in uninfected mice to 33 and 27%, respectively, at 15 DAI. This rise was stimulated in Ts-infected mice predominantly by adult Ts. In the MLN of Nb-infected rats, the percentage of cells that were sIgE+ was greater than 50% at 15 DAI. However, there was no detectable increase in sIgE+ cells in the spleen and MLN of Sm-infected mice until 5 WAI; peak levels of approximately 20% sIgE+ cells were reached at 8 WAI. Treatment of MLN cells from mice infected with Nb, Ts or Sm and rats infected with Nb, with pH 4.0 acetate buffer for 1 min (acid treatment) removed all detectable sIgE from greater than 90% of the sIgE+ cells, but did not remove sIgD or sIgM from cells with these surface isotypes. The effect of acid treatment on sIgE was similar even after a secondary infection of mice or rats with nematode larvae. These data show that helminthic infection, in general, is a potent stimulator of the IgE system at the cellular level and that almost all of the sIgE+ cells that arise have acquired cytophilic sIgE.

In vivo blockage of B cell maturation by splenic T cells of total lymphoid irradiated mice

The effect of fractionated total lymphoid irradiation (TLI) on the induction of cells blocking in vivo B cell maturation was examined. (BALB/c x C57BL/6)F1 mice received 200 rds lymphoid irradiation daily for 8 days. One month after termination of the irradiation splenic T cells of TLI-treated mice were transferred, together with normal bone marrow cells, to lethally irradiated hosts. In addition, splenic cells or splenic B cells of TLI mice were transferred to irradiated hosts. Two months later, we checked the reconstituted mice for their ability to produce in vivo anti-trinitrophenyl (TNP)-Ficoll antibodies and their capacity to respond in vitro to dextran sulfate and lipopolysaccharide. In parallel, stained spleen cells were analyzed on the fluorescence-activated cells sorter using monoclonal anti-mu, anti-delta and anti-B220 surface marker antibodies. The results indicate that splenic T cells originating from TLI-treated mice cause maturation arrest of normal and TLI-treated B cells, since normal bone marrow cells injected together with those cells have immature phenotypic and functional features. In addition, neither splenic cells nor splenic B cells of TLI-treated mice can mature upon transfer to normal irradiated hosts. The B cells are IgM+, IgD-; they respond with a high proliferation rate to dextran sulfate and low proliferation rate to lipopolysaccharide, and poorly to TNP-Ficoll challenge.

Activation of mouse lymphocytes by anti-immunoglobulin. IV. Stimulation with soluble heterologous anti-delta antibodies

Mouse spleen cells were stimulated to proliferate in vitro by soluble affinity-purified heterologous antibodies to mouse delta. Antibodies from goat or rabbit antisera to TEPC 1017, a mouse IgD myeloma protein, were purified on an affinity column of TEPC 1033, a second mouse IgD myeloma protein. Maximum uptake of [3H]thymidine in the range of 60,000 cpm was obtained after 48 hr of culture with anti-delta at concentrations of 50 micrograms/ml. In contrast, the hybridoma 10-4.22 anti-delta was nonmitogenic at similar concentrations. The proliferative response was not impaired upon removal of T cells by treatment with an anti-thymocyte serum (ATS), nor by removal of adherent cells by passage of spleen cells over Sephadex G-10 columns and counter-flow centrifugation. Splenic lymphocytes isolated on the fluorescence activated cell sorter (FACS) with intermediate-to-high amounts of surface IgD (sIgD) were responsive to soluble anti-delta, while IgD-negative cells, or cells with low amounts of sIgD, were unresponsive. Spleen cells from mice less than 4 weeks of age, or from mice carrying the X-linked B cell defect (xid), were unresponsive to anti-delta. These results indicate that anti-delta acts similarly to anti-mu in stimulating a proliferative response by later maturing B cells, which are characterized by a high density of sIgD.

Maturation of the lymphoid system. IV. Ontogenetic compartmentalization of T cell function

Pretreatment of one day old but not eight day old or adult A/J mice with soluble ovalbumin (OVA) initiated specific T-cell unresponsiveness as reflected both in T-cell dependent cellular proliferation and in anti-hapten antibody responses to dinitrophenyl-OVA. In contrast, injection of soluble human gamma globulin into either neonatal or adult A/J mice resulted in unresponsiveness. The ability of lymph node T-cells to be sensitized by protein antigens occurred shortly after birth, since the degree of sensitization in 9 and 26 day old mice was similar. Finally, a striking ontogenetic difference was noted in the capacity of lymphocytes derived from the lymph nodes and spleens of young mice to respond to T-cell mitogens. Thus, while splenocytes obtained from 9 day old mice exhibited meager responses to PHA and Con A, lymph node cells from these animals responded at nearly adult levels. These observations are interpreted as reflecting an ontogenetic and tissue-specific division of T-cell function.

Modulation of B and T cell subsets in mice treated with fractionated total lymphoid irradiation. II. Tolerance susceptibility of B cell subsets

Total lymphoid irradiation (TLI) results in long-lasting changes in the characteristics of both T and B cells suggestive of arrested maturation. A characteristic feature of immature B cells is their high susceptibility to tolerance induction. This study examines the susceptibility to tolerance to bovine serum albumin (BSA) of TLI-treated mice. Two experimental protocols were designed. In the first, tolerance to BSA was induced in TLI-treated adult (BALB/c X C57BL/6)F1 mice, and the ability of B cells of those mice to respond to BSA was assessed in an adoptive transfer system. In the second experimental protocol, tolerance was induced in adoptive hosts reconstituted with purified B cells originating from TLI-treated mice and with splenic T cells of normal, untreated mice. Results obtained in these two systems clearly demonstrated that splenic B cells of TLI-treated mice are highly susceptible to tolerance induction. This high susceptibility of B cells is linked neither with the elevation of immature T cells nor with induced T suppressor cells which arise due to the long-term malfunction of the thymus. Tolerance could be induced in TLI cells even 4 months after termination of the treatment. Thus, maturation processes of B cells in TLI-treated mice are arrested for long periods of time.

Modulation of B and T cell subsets in mice treated with fractionated total lymphoid irradiation. I. Blockage of differentiating B cell pathways

The effect of fractionated total lymphoid irradiation (TLI) on the maturation of B cells was examined in mice. At various times after irradiation of the mice, their spleen cells were tested for the mitogenic responses to dextran sulfate and lipopolysaccharide. In parallel the cells were stained with fluorescent anti-Thy-1 and various anti-Ig antisera, and were analyzed on a fluorescence-activated cell sorter (FACS). By comparison with normal spleen cells the cells of TLI-treated mice gave a high response to dextran sulfate and a low response to lipopolysaccharide. FACS analysis revealed that TLI-treated spleen contains elevated numbers of B cells bearing high IgM and low IgD on the surface. The B cells of TLI-treated mice retained these immature characteristics even two to four months after the last irradiation. These findings indicate that TLI causes a longlasting blockage in B cell maturation processes.

Heterogeneity of complement receptor expression on surface immunoglobulin-bearing cells from neonatal and adult mice

The ontogeny of acquisition of complement receptors (CR) on splenic B lymphocytes from mice of varying ages was examined. Reagents used for the identification of CR included antibody- and complement-coated erythrocytes (EAC), bacteria (BAC) and bacteria treated with complement alone (BC). When whole mouse serum used as the source of complement both EAC and BAC failed to bind to human erythrocytes (C3b receptor-negative), showed binding to Raji and Daudi cells (C3d receptor) and formed rosettes with human neutrophils (C3bi receptor). Therefore these reagents bore C3d and C3bi, but not intact C3b. Although EAc and BAC detected nearly equal percentages of CR lymphocytes in adult mice, BAC bound to a higher percentage of neonatal lymphocytes (8-12%) than did EAC (1-3%). The ability of BAC to detect EAC-negative lymphocytes among neonatal spleen lymphocytes appeared to be due to the increased sensitivity of this bacterial reagent for binding to CR. Further evidence of this enhanced sensitivity was that BAC were less inhibitable than EAC by soluble antigen-antibody-complement complexes.

Characterization of the bone marrow cell population expressing an AKR murine leukaemia-virus gp71-like antigen

The murine bone marrow population mainly responsible for the unique competing activity of this lymphoid organ in the competition radioimmunoassay (cRIA) for AKR murine leukaemia viruses gp71 has been partially purified and characterized. That population could be distinguished by the following properties: (i)gp71+ cells (cell population expressing the AKR MuLV gp71 antigen) are mainly medium density cells, according to their distribution in the layers of a discontinuous bovine serum albumin (BSA) gradient; (ii) The gp71 positive cells are not mature lymphocytes; (iii) This cell population is found both in the FcR+ and FcR- compartments and is not included in the complement (C') receptor-positive population; and finally, (iv) the gp71+ cells are phagocytic cells and an adherent cell population according to its capacity to adhere to plastic surfaces, nylon wool and Sephadex G-10.

Sandwich radioimmunolabeling for the study of surface properties of bone marrow lymphocytes

A modification of sandwich radioautographic method was applied to the study of surface immunoglobulin and/or specific antigens on small lymphocytes in mouse and human bone marrow. After incubation of marrow cell suspensions at 37 degrees C, cells were reacted at 0 degree C for 30 min with graded dilutions of rabbit anti-mouse or anti-human immunoglobulin followed by further reaction with a sheep anti-rabbit immunoglobulin labeled with 125I. Detectable surface immunoglobulin was demonstrated in approximately one-third of mouse marrow lymphocytes and 20-25% of human marrow lymphocytes. The densities of surface immunoglobulin as assessed by grain counts on individual labeled lymphocytes tended to be lower in the marrow than in spleen or peripheral blood. When the same rabbit antiserum was used to compared the sensitivity of the sandwich method with that of the direct radioautography, the former was found sufficiently sensitive to give a plateau level of labeling without seriously increasing background grains. The advantages of the method are discussed with reference to studies on T and B cells specific antigens on human bone marrow lymphocytes.

In vitro and in vivo response of lymphoid cells from LHC hamsters to murine thymus-independent and thymus-dependent antigens

Lymphoid cell populations (spleen, lymph node, peripheral blood, thymus, and bone marrow) from LHC inbred hamsters were studied in order to characterize further the immune response of this species. The direct PFC response to several thymic-dependent or thymic-independent antigens was evaluated. A specific direct PFC response occurred 4 days after immunization with SRBC, DNP-BSA, DNP-lys-Ficoll, TNP-LPS, TNP-BA, and SSS-III. Attempts to induce a polyclonal antibody response with LPS, TNP-LPS, SSS-III, and DNP-lys-Ficoll were unsuccessful. A weak polyclonal response was induced with TNP-BA. Spleen cells and PBL responded strongly in vitro to the T-cell mitogens Con A and PHA-P, but gave weak and inconsistent responses to the B-cell mitogens LPS and PI-PC. LHC hamster lymphoid cell populations bore sIg and receptors for C3 (EAC rosettes) in approximately the same ratio as various murine species. However, the profile of the number of cells bearing low-to-intermediate densities of sIg differed significantly from those of murine species when analysed with the FACS. There was a sharp reduction in the number of cells with low-to-intermediate densities of sIg. These data suggest that B cells in this strain and species lack the ability to translate signals which lead to polyclonal antibody synthesis or lack the appropriate populations of B cells that have membrane receptors for mitogens which are thought to induce such activity in murine systems and provide evidence for separate signals that induce thymus-independent and mitogenic responses. The importance of this model for studying mechanisms involved in B-cell activation is discussed.

Intracytoplasmic immunofluorescence in multiple myeloma

A new intracytoplasmic immunofluorescence staining procedure has been investigated to detect and quantify myeloma cells by means of flow cytometry. Freshly harvested bone marrow aspirations from 12 patients with multiple myeloma were treated with collagenase and Triton X-100, and incubated with different specimens of fluoro-isothiocyanate-marked antihuman immunoglobulins. DNA-staining was then done with propidium iodide. Biparametric evaluation in a cytofluorograph 6300A/FC 200 showed a characteristic cluster distribution of normal and pathological immunoglobulin-producing cells. This intracytoplasmic fluorochromic staining procedure may be significant for the specific identification of nonsecretive immunocytomas, which cannot be detected by serodiagnostic methods.

Effect of silica on the innate resistance of inbred mice to Salmonella typhimurium infection

The role of macrophages in the innate immunity of (CBA/N female X DBA/2N male)F1 female mice to Salmonella typhimurium was assessed with silica, an agent which has been reported to selectively inactivate macrophages. Silica, administered intravenously to mice, markedly decreased the phagocytic capacity of splenic macrophages but had no effect on splenic responsiveness to the B-cell mitogen lipopolysaccharidide or the T-cell mitogen phytohemagglutinin, nor did it affect the frequency of surface immunoglobulin-positive cells (B cells). Silica given to mice 1 day before intraperitoneal challenge decreased the 50% lethal dose of S. typhimurium 100-fold. The incidence of survival of mice given silica up to 14 days before infection with a sublethal dose of organisms was also decreased. This susceptibility could also be demonstrated when silica was given 10 days, but not 20 days, after S. typhimurium infection. Poly-2-vinylpyridine-N-oxide, a lysosomal stabilizing agent, abrogated the silica effect. Deaths among silica-treated mice followed uncontrolled multiplication of the organism in the spleen. These results provide direct evidence that macrophages play an essential role in natural immunity to murine typhoid and demonstrate the efficacy of silica as a tool to analyze macrophage function.

The response to lipopolysaccharide of mouse spleen lymphocytes fractionated on the basis of surface immunoglobulin and complement receptor using fluorescence-activated cell sorting and rosetting techniques

Mouse spleen lymphocytes were stained with rabbit antisera specific for either μ chain or δ chain, followed by fluorescein-conjugated goat anti-rabbit immunoglobulin. The cells were analysed and fractionated using a fluorescence-activated cell sorter. Fifty-five per cent of the lymphocytes stained with a polyspecific anti-Ig reagent or with a combination of anti-μ and anti-δ reagents, while about 40% of the lymphocytes were stained when either the anti-μ reagent or the anti-δ reagent was used alone. Three per cent of the lymphocytes stained with the anti-μ reagent, but not with the anti-δ reagent, and eight per cent stained only with the anti-δ reagent. Unfractionated spleen cells and populations depleted of μ- or δ-bearing cells were cultured in the presence of lipopolysaccharide. All three populations responded by incorporating [³H]-thymidine and secreting IgM and IgG.

Spleen cells were fractionated by a rosetting technique into complement receptor-positive and negative populations. Both populations were able to respond to lipopolysaccharide and to synthesize Ig of both the IgM and IgG classes. Unfractionated cells and complement receptor-negative populations were stained for surface μ or δ chain and analysed on the fluorescence-activated cell sorter. The distribution of staining intensity suggested that the complement receptor-bearing population was enriched in cells which stain weakly for μ and cells which stain with a low to intermediate intensity for δ chain.

It is concluded that the precursors of IgM- and IgG-secreting cells are not limited to any one of the three populations of cells defined on the basis of surface immunoglobulin or to either of the populations defined on the basis of the complement receptor.

Density of surface immunoglobulin and capping on rat B lymphocytes. I. Changes with aging

The rate of capping and shedding of cross-linked surface immunoglobulins (SIg) was slower in old Lewis rats (greater than 24 mo) than in young Lewis rats (3-4 mo). Analysis of spleen cell populations with the fluorescence-activated cell sorter indicated that with aging there was a loss of cells with a high density of SIg. Cells with the highest density of SIg capped and shed cross-linked SIg faster than cells with a low density of SIg. The alteration in density of SIg may account for the difference in capping kinetics. Colchicine treatment increased the rate of capping of lymphocytes from young animals, but had no effect on the capping kinetics of lymphocytes from old animals.

Maturation of B lymphocytes. II. Sequential appearance of increasing IgM and IgD in the adult bone marrow

The relationship between surface IgM (sIgM) and surface IgD (sIgD) was examined on small lymphocytes in the adult murine bone marrow or prepubertal spleen. Cells were sorted on the basis of different sIgM levels by a fluorescence-activated cell sorter (FACS) and relabeled for sIgD or total sIg by a sandwich technique using 125I-labeled protein A and radioautography. For detecting sIgD, an anti-delta allotype reagent was used in congenic mice. Cells lacking sIgM in the bone marrow or spleen were also found to be sIgD-; thus, sIgD appeared only in the presence of sIgM. Weak sIgM-bearing cells in the bone marrow also had no sIgD indicating that sIgD appeared only after the acquisition of a significant level of sIgM. Subsequently, the incidence of sIgD+ cells increased in fractions showing increasing sIgM levels indicating the acquisition of new sIgD by "sIgM only" cells with increasing maturation levels in the bone marrow. In marrow lymphoid cells expressing both Ig isotypes, sIgM and sIgD levels increased in parallel, possibly with increasing maturation level. In the spleen, the incidence of sIgD+ cells among various cell fractions showing different sIgM levels was found constant. However, spleen cells bearing both receptors, showed a small increase in the sIgD level with increasing sIgM level.

Activation of mouse lymphocytes by anti-immunoglobulin. II. A thymus-independent response by a mature subset of B lymphocytes

Mouse spleen cells can be stimulated to proliferate in vitro by purified anti-mu or anti-gamma,kappa antibodies. These responses can be obtained in cell populations bearing membrane immunoglobulin (Ig), purified by the fluorescence activated cell sorter (FACS), but they are not observed in FACS-purified Ig- cell populations. Furthermore, treatment of spleen cell populations with anti-Thy 1.2 and complement does not impair the response, nor does addition of nylon wool-purified T lymphocytes enhance it. These results indicate that B lymphocytes respond to anti-Ig and that their response does not require T cells. On the other hand, cells from athymic nude (nu/nu) mice respond slightly less well to anti-mu than do cells from heterozygous littermate (nu/+) controls; nu/nu cells are almost unresponsive to anti-gamm,kappa and addition of nylon wool-purified T cells from nu/+ controls does not restore the response. This suggests that T lymphocytes or the thymus may control the appearance of cells responsive to anti-gamma,kappa. Responsiveness of normal mice to anti-mu does not appear until 4 wk of age and does not reach maximum levels until 8 wk of age. Acquisition of full responsiveness to anti-gamma,kappa is even more delayed. This, together with the failure of mice with the CBA/N B-cell defect to respond to anti-Ig, suggests that cells stimulated to proliferate by anti-Ig are a mature subset of B cells. Depletion of adherent cells by Sephadex G-10 treatment or by treatment with carbonyl iron and exposure to a magnetic field does not diminish anti-mu or anti-gamma,kappa responses, suggesting that the responsiveness does not require the presence of macrophages. Thus, activation of B-cell proliferation by anti-Ig appears to be a T-cell independent, macrophage-independent process in which membrane Ig plays a direct role in signal generation.

Maturation of bone marrow lymphocytes. II. Development of Fc and complement receptors and surface immunoglobulin studied by rosetting and radioautography

Radioautographic DNA labeling and rosetting techniques were combined to study the development of surface IgM, Fc, and complement receptors (FcR, CR) on small lymphocyte populations in mouse bone marrow. [3H]thymidine was either infused continuously to label newly formed cells for periods up to 4 days, or injected daily, 21--35 days before use, to label a sample of long-lived cells. Bone marrow cells were incubated with sensitized sheep erythrocytes to detect surface IgM, FcR, and CR, respectively, and examined radioautographically after cytocentrifugation. During [3H]thymidine infusion, marrow small lymphocytes lacking surface markers were the first to show [3H]thymidine labeling. Most of these cells became labeled by 4 days (IgM--ve, 89%; FcR--ve, 92%; Cr--ve, 88%). Labeling of small lymphocytes bearing surface IgM, FcR, and Cr began after an initial lag and increased to high values by 4 days (IgM + ve, 73%; FcR + ve, 82%; CR + ve, 83%). Labeled IgM + ve small lymphocytes formed progressively larger rosettes as cell age increased. Some proliferating large lymphoid cells formed rosettes for IgM, FcR, and CR. Labeled long-lived small lymphocytes expressed surface IgM, FcR, and CR, the incidence of each receptor being uniformly high (38--43%) and the rosettes tending to be larger than those formed by newly formed lymphocytes. In double-surface marker studies, FcR and CR rosettes were formed by some IgM--ve small lymphocytes as well as IgM + ve cells in the marrow. After transfusion of marrow cells from donor mice infused with [3H]thymidine for 24 h, many labeled newly formed lymphocytes homed into the splenic red pulp of unlabeled syngeneic recipients. Subsequently, these cells showed a rapid increase in the incidence of rosettes for surface IgM, FcR, and CR, together with a progressive enlargement of each type of rosette. Although all the labeled small lymphocytes recovered from the spleen developed both surface IgM and FcR by 3 days, only approximately one-half developed CR. The results demonstrate that most of the small lymphocytes bearing FcR, CR, and surface IgM in mouse bone marrow are newly formed indigenous cells. Each receptor becomes detectable by rosetting soon after the small lymphocytes are first produced. The newly formed, marrow-derived small lymphocytes are able to continue their development of surface IgM, FcR, and CR after migrating into the spleen, consistent with a maturation of primary B lymphocytes. In addition, the data indicate the genesis in mouse marrow of a non-B lineage of lymphocytes (notably, IgM--ve FcR + ve cells.). A minority of small lymphocytes bearing IgM, FcR, and CR in mouse marrow are long-lived cells, presumptive recirculating immigrants, differing in receptor status from the newly formed cells. The results are discussed with regard to the heterogeneity of marrow lymphocytes and proposed models of primary B lymphocyte and null lymphocyte production.

Age-dependent variations of antibody avidity

Age-dependent variations of antibody avidity were studied in the C3HeB/FeJ mouse. Spleen cells from donors of different ages (10--720 days) were transferred and stimulated with TNP-HRBC in lethally irradiated syngenic recipients. The anti-TNP antibody response of the donor cells was estimated from the number of direct PFC per recipient spleen by the Jerne technique with TNP-SRBC. Avidity of the antibodies secreted by PFC was evaluated from the amount of added TNP-BSA that inhibited 50% of the anti-TNP PFC. Under these experimental conditions allowing the exclusion of any influence of the donor milieu during the immune response, age-dependent variations of the antibody response and avidity could be attributed to changes in the donor spleen cell population. Avidity was found to increase with the response and to vary parabolically with age. After appropriate correction of the number of PFC to make it independent from age, avidity values were fitted by a multiple curvilinear regression in which the independent variables playing a significant role were the corrected number of PFC in its linear term and the age in its linear and quadratic terms. From comparison of the standard coefficients of this regression, the observed variations of avidity could be attributed in part (82%) to the response and in part (18%) to the age. For any value of response, avidity increased 15-fold from day 10 to reach a maximum at day 110 and then declined 5-fold at the age of 720 days. Heterogeneity of avidity also changed parabolically with age as high avidity classes were present in adulthood and absent at 10 and 720 days.

Ontogeny of murine-B-lymphocytes. Avidity of antigen binding cells in neonatal and adult mice

The heterogeneity of avidity of DNP-binding (rosetting) cells has been studied in mice of various ages, in an attempt to learn more about the development of antibody diversity. The results indicate that during the neonatal period murine B cells show a limited heterogeneity of avidity with no "high" avidity ABC being detectable. This implies that the full repertoire of anti-DNP antibodies is only gradually acquired during ontogeny. The results are interpreted as favouring the hypothesis that somatic events are important in the generation of antibody diversity.

Cellular and molecular requirements for X-linked, hapten-specific B-cell blockade in CBA/N mice

CBA/N mice, a mutant CBA subline, harbor an X-linked B-cell defect which prevents them from mounting immune responses to certain thymic-independent antigens such as pneumococcal polysaccharides and haptenated-Ficoll derivatives. These mice and the hybrid male progeny of CBA/N females are also exquisitely sensitive to a hapten-specific blockade of their otherwise adequate immune responses to thymic-dependent antigens such as N-2,4-dinitrophenylated-hemocyanin (DNP-KLH). As little as 10 ng of a DNP-Ficoll conjugate given 2 h before immunization with a 5,000-fold greater dosage of DNP-KLH, virtually abolishes the 4th-day direct plaque-forming cell (PFC) response specific for DNP. Responding hybrid (CBA/N x C3H/HeN) female mice are resistant to such blockade even at DNP-Ficoll dosages increased by three orders of magnitude. The DNP hapten and Ficoll must be chemically joined for this blocking effect to occur, and increasing the hapten derivatization of Ficoll increases its blockade-invoking capacity. Significant blockade can be produced by administering DNP-Ficoll as early as 4 days before or as late as 4 h after immunization with DNP-KLH. All currently available data point to the defective B cell as the target of this hapten-polysaccharide-mediated blockade. Mice bearing B memory cells, however, are refractory to such blockade. In addition, DNP-Ficoll injections which cause virtually total blockade of 4th-day primary direct PFC responses to DNP-KLH have little or no effect on the development of DNP-reactive B-cell memory measured at either 8 or 30 days. These findings suggest very different blockade susceptibilities for B cells or their precursors at various stages of differentiative development. Our findings also lead to the formulation of testable hypotheses regarding the mechanism of this selective B-cell blockade phenomenon.

Ontogeny of B lymphocytes in mice. Quantification of surface membrane immunoglobulins by immunoperoxidase assay

Surface membrane immunoglobulins (SmIg) of splenic lymphocytes were investigated by immunoperoxidase assay in newborn Swiss mice, their mothers and adult controls. The mean number of SmIg + cells in adult mice was 45-8% and the mean number of antigenic sites per positive cells was 108,500. In newborn mice during the first 7 days of life, values for both parameters were low (24-25--28-5% and 38,000-45,773 respectively) and began to rise after the 10th day to reach adult levels between the ages of 2 and 3 weeks. A peak above adult levels for the mean number of sites per cell was observed on day 21 with a subsequent drop to adult levels on day 28. Post-partum females were found to have consistently fewer sites per positive cell (69,000-86,600) during the 14 days following delivery than their adult control counterparts, though the difference was not statistically significant.