Helper factors for hapten-self cytotoxic T cells occur in NZB culture supernatants despite deficient AMLR

The ability of helper T cells from NZB mice to produce non-interleukin 2 (IL-2) lymphokines in the autologous mixed lymphocyte reaction (AMLR) was examined. Factors present in normal AMLR culture have been previously reported to mediate the development of a cytotoxic T-cell response to trinitrophenyl (TNP)-modified syngeneic thymocytes. Young NZB mice, like the normal strains, were able to produce the helper factors in the AMLR and to utilize these mediators in the cytotoxic induction system. Old autoimmune NZB mice demonstrated a poor proliferative response in the AMLR and were unable to activate hapten-specific cytotoxic cells in the presence of AMLR culture supernatant from either young or old mice. This was not due to a lack of cytotoxic precursors, nor was it a normal consequence of aging, but may be related to decreased IL-2 production by helper T cells. Interestingly, supernatant from AMLR proliferation deficient old NZB mice contained normal amounts of the AMLR helper factor. These data suggest that AMLR helper factor production is not directly related to the proliferative response and that two different helper-T-cell subpopulations may be responsible for these activities. The production of these mediators in mice which cannot utilize them raise questions about their role in autoimmunity.     

Spontaneous proliferation in unfractionated spleen cell cultures: autologous mixed-lymphocyte reactions (AMLR) which can be differentially regulated by prostaglandins and lymphokines

The present studies were undertaken to define the contribution of the autologous or syngeneic mixed-leukocyte reactions (AMLR/SMLR) to the cellular proliferation observed in unfractionated spleen cell cultures. Proliferation was studied in whole, untreated 6-day murine spleen cell cultures supplemented with syngeneic serum. These cultures exhibited relatively low but significant levels of cellular proliferation as measured by uptake of radioactive thymidine ([3H]TdR). Treatment of spleen cells with monoclonal anti-Thy 1.2 antibody and complement before culture, the addition of specific anti-I-A monoclonal antibodies to the cultures or removal of Ia+ adherent cells before initiation of culture all inhibited the proliferative response significantly. Thus, the autologous proliferation of untreated and unfractionated spleen cells manifests the main characteristics of the AMLR/SMLR, namely, its dependence on T (responder) and Ia+ (stimulator) cells and specific inhibition by anti-I-A antibodies. A marked augmentation in cellular proliferation was observed in unfractionated spleen cell cultures treated for the initial 24 hr of culture with 5 X 10(-6) M indomethacin, an inhibitor of prostaglandin synthesis. Conversely, the addition of 7 X 10(-9) M prostaglandin E1 (PGE1) to these cultures depressed cellular proliferation. This suppression of autologous splenic cell proliferation induced by PGE1 could be partially reversed by the addition of concanavalin A-induced lymphokine (LK) preparations early in the culture. These findings indicate that (a) the proliferation of unfractionated spleen cell cultures occurring in the absence of exogenous stimulatory signals is due largely to an ongoing AMLR, and (b) biologically active mediators with opposing influences, namely, prostaglandins and immunostimulatory LK, participate in the regulation of the AMLR.     

The role of Ia antigens and Fc receptor-bearing T-cells in the inhibition of macrophage receptors for cytophilic antibody induced by soluble immune complexes

Soluble antigen-antibody complexes composed of 3 M KCl-extracted L1210 antigens and alloantibody to L1210 given to C3H mice caused immunosuppression in the mice. This was reflected in part by the inhibition of cytophilic antibody receptors on macrophages which could be used as a measure of the suppression. Thymocytes or splenic T cells from mice treated with immune complexes could adoptively transfer the suppression to normal syngeneic mice. These cells, which we have termed suppressor inducers, were found to be Ia positive: specifically, I-A⁺, I-J^?. Thus, treatment of the inducers with anti-la or anti-I-A antibodies and complement in vitro abrogated their ability to transfer the suppression to normal mice. In contrast treatment with anti-I-J serum and complement had no effect. Through a similar approach, the cooperating (acceptor) T cells were found to be I-A⁺, I-J^?. Pretreatment of mice with anti-Ia or anti-I-A serum before the administration of antigen-antibody complexes prevented the inhibition of macrophages. This was due at least in part to steric hindrance of adjacent Fc receptors on the FcR⁺ T cells with which the complexes interacted. Early interaction of immune complexes with FcR⁺ T cells was in fact demonstrated directly by the inability of the complexes to induce suppression when FcR⁺ T cells were depleted. The thymocytes or splenic T cells from anti-Ia-pretreated mice failed to transfer the suppression to recipient mice. In contrast, treatment with either anti-Ia or anti-I-A after the immune complexes did not abrogate the generation of suppressor inducers. Treatment of normal recipient mice with anti-Ia serum in vivo before they received the suppressor inducer cells did not prevent cooperation between the two types of cells. By the same token, blocking of Ia antigens of the inducers in vitro with anti-Ia serum (without complement) also did not impair the cooperative interaction. These results indicate that antigen-antibody complexes generate I-A-positive, I-J-negative T-suppressor inducer cells from FcR⁺ naive T cells. These in turn interact with Ia-positive (I-A⁺ and I-J^?) normal thymocytes or spleen T cells. This interaction most likely generates the ultimate suppressor T cells that suppress cytophilic antibody receptors on macrophages in vivo. However, the I-region determined antigens did not appear to be directly involved in the T-T interaction of suppressor inducer and acceptor cells.     

Splenocytes from NZB mice exhibit spontaneously high rates of fusion compared to control strains

A previous report (G. E. Woloschak and D. Senitzer, submitted for publication) has demonstrated that mitogen-stimulated splenocytes fuse at a much higher frequency than untreated splenocytes as measured by the fusion index (a calculation of the number of nuclei in fused cells vs the total number of nuclei). A measurement of the fusion indices of NZB spleen cells provides results markedly different from those observed with splenocytes from control strains of mice—NZB spleen cells exhibit a spontaneously high fusion index. In this assay, they spontaneously display the same fusing capacity as that observed in cultures of mitogen-treated spleen cells from control strains of mice. This elevated fusion index is not affected by treatment with anti-Thy-1.2 and complement, but is abrogated by treatment with anti-immunoglobulin serum and complement. This suggests that a B cell is responsible for the high fusion index of NZB splenocytes. This high fusion index is present when using splenocytes from both male and female mice in the fusion assay, and can be observed using spleen cells from NZB mice as young as 12 days. This appears to be the result of a spontaneous polyclonal B-cell activation in NZB mice.     

T lymphocytes responding to Mls-locus antigens are Lyt-1+, 2− andI-A restricted

We have investigated primary and secondary responses of mouse splenic T cells to strong mixed lymphocyte stimulating antigens controlled by theMls locus using MHC-identical mixtures of cells. Our studies show that strong primaryMls-locus specific responses involve recognition of self I-A antigens, since BUdR and light suicide or F1 into parent radiation bone-marrow chimeras both demonstrate a preference of unprimed F1 T cells to respond to Mis-locus antigens associated with one parent's MHC antigens. Furthermore, conventional anti-I-A antisera and monoclonal anti-I-A antibody both inhibitMls-locus responses in an MHC-specific manner. Finally, as is typical of T cells responding to I-A antigens or to nominal antigens associated with self I-A,Mlslocus responses are mediated by Lyt-1⁺, 2^– cells. One striking finding in these studies was the very high frequency of cells capable of responding to Mls-locus antigens, the highest being 1/300 splenic T cells. This plus evidence for recruitment during primaryMls-locus responses may account for reports of a lack ofI-A restriction in secondary anti-Mls locus responses to strong Mls-locus antigens, a finding with which we concur. The possibility that these secondary responses between noncongenic strains of mice may be directed at other genetic loci is also discussed. These experiments leave open the question of the biological role of theMls-locus and of the very large number of T cells reactive to it.Abbreviations used in this paper MHC Major histocompatibility complex - MIg Mouse immunoglobulin - MLC Mixed lymphocyte culture - TCGF T-cell growth factor     

Role of T cells in regulating expression of the B cell repertoire. Anti-ssDNA precursor frequency of DBA/2 B cells is increased in the presence of T cells from NZB mice

Splenic B cells from DBA/2 and NZB mice were compared with regard to precursor frequency of anti-ssDNA-producing cells. Using a modification of the splenic fragment assay, we show that NZB T cells are capable of increasing the frequency of expression of anti-ssDNA precursors in DBA/2 splenic B cells. When limiting numbers of splenic B cells of DBA/2 origin were adoptively transferred into an irradiated (1200 rad) recipient, the co-transfer of NZB T cells markedly increased the frequency of anti-ssDNA precursors in cultured splenic fragments. The anti-ssDNA produced under these conditions was exclusively IgM and exhibited a high degree of cross-reactivity with TNP and fluorescein. Thus, the increase in anti-ssDNA precursor frequency reflected an expansion of the B cell repertoire to include precursors of polyspecific antibody-producing cells that under normal circumstances are not expressed. The ability of NZB T cells to increase the anti-ssDNA precursor frequency was further defined by the CBA/N immunodeficiency gene xid, in that B cells from DBA/2.xid donors did not exhibit increased anti-ssDNA precursor frequency in the presence of NZB T cells. When NZB splenic B cells were co-transferred with DBA/2 T cells, the anti-DNA precursor frequency of the NZB B cells was not reduced. This study demonstrates that T cells can influence the emergency of B cell clones in an Ag-nonspecific manner. The well documented in vivo spontaneous polyclonal activation of NZB B cells may be secondary to T cell-mediated expansion of the B cell repertoire.     

Influence of sex hormones on Coxsackie B-3 virus infection in Balb/c mice

Background and “spontaneous” proliferation are terms often used for the proliferative activity normally exhibited by peripheral blood mononuclear cells (MNC) in vitro. In this report, we show that Interleukin-2 (IL-2) added to unfractionated MNC but not to isolated T or non-T cells significantly increased their proliferative activity. The cells responding to IL-2 stimulation from MNC were OKT3 positive lymphocytes. In addition, treatment of MNC with either a monoclonal anti-HLA-DR antibody (in the absence of C′) or Cyclosporin-A strongly suppressed the “background” whereas treatment of MNC with the 3A1 monoclonal anti-human T cell antibody did not modify “spontaneous” proliferation of these cells. IL-2 could not restore or increase the proliferative activity of MNC exposed to the anti-HLA-DR antibody or Cyclosporin-A while the T cell growth factor significantly enhanced proliferation of MNC cultured in the presence of the OKT4 antibody. Taken together these results strongly suggest that IL-2 responding T cells from MNC become sensitive to IL-2 by interacting with HLA-DR antigens on B lymphocytes and/or monocytes contained in MNC (resting T cells are Dr^?). By a similar mechanism we have previously shown that T cells acquire responsiveness to IL-2 in the autologous mixed lymphocyte reaction (AMLR). Since all the cells that participate in AMLR are present in MNC, we postulate that a “mini” AMLR taking place within MNC may explain the “spontaneous” proliferation of peripheral blood mononuclear cells.     

The autologous mixed lymphocyte reaction in strains of mice with autoimmune disease

We have studied the autologous mixed lymphocyte reaction (AMLR) in 3 strains of mice with autoimmune disease. T cell proliferation to autologous non-T cells occurs in young mice of these 3 strains (as it does in normal mice) but is absent or greatly reduced in older mice of strains with autoimmune disease. Reciprocal mixing experiments revealed that the defect in the AMLR of the older mice resides in the responder T cell population. Further analysis of the cells participating in the AMLR of young mice of the B/W F1 strain revealed that: 1) a Thy 1- and Ly1-positive responder cell was necessary at the start of the culture to initiate the AMLR; 2) the cells present after 5 days of culture contained very few, if any, Ly123 cells in the B/W F1 strain compared with the normal C57BL/6 strain; and 3) the stimulating cell appear to be a macrophage, and an Ia-bearing cell must be present for the reaction to occur.     

Syngeneic mixed lymphocyte reaction in mice: strain distribution, kinetics, participating cells, and absence in NZB mice.

Co-culture of mouse spleen nonadherent (T-enriched cells with mitomycin C-treated unfractionated syngeneic spleen cells resulted in increased DNA synthesis in the responding T cells. The kinetics of this syngeneic mixed lymphocyte reaction (SMLR) showed that peak DNA synthesis occurred on day 5 of culture compared to day 4 for conventional mixed lymphocyte reaction (MLR). Anti-T cell antiserum plus complement treatment of the responding cell population abolished the reaction, and similar treatment of the stimulator population enhanced SMLR. These studies indicate that SMLR represents the response of T cells to non-T cells. Studies on the generation of cytotoxic T lymphocytes (CTL) in parallel cultures of T cells activated by syngeneic or allogeneic spleen cells showed no cytotoxicity of SMLR-activated cells for either PHA- or LPS-induced blasts but did show a good CTL response of allo-activated cells to both targets. Studies on the strain distribution of SMLR revealed that NZB mice manifested poor or no stimulation in SMLR whereas all other strains tested exhibited strong SMLR. This defect in NZB mice may be pathogenetically related to the autoimmune disease that develops in these mice.     

Heterogeneous lymphokine-activated killer cell precursor populations

Summary We developed a monoclonal antibody (mAb) 211, which recognizes the precursors in peripheral blood of lymphokine-activated killer cells (LAK) induced by recombinant interleukin-2 (rIL-2). In conjunction with complement mAb 211 also eliminates natural killer cells (NK) and a majority of the cytotoxic T lymphocytes. B cells and monocytes do not express the 211 antigen. Since mAb 211 recognized such a large percentage of peripheral blood lymphocytes we examined which 211⁺ subpopulation was the predominant precursor of rIL-2-induced LAK cells using two-color fluoresence-activated cell sorting (fluorescein-conjugated 211 mAb plus phycoerythrin-CD11b). This method identified the 211⁺/ CD11b⁺ population as the predominant phenotype of the rIL-2-induced LAK precursor. In addition, we directly compared the phenotype of the LAK precursor induced by delectinated T-cell growth factor (TCGF) to that induced by rIL-2. The 211-depleted population, which was devoid of NK cells and LAK precursors (inducible by rIL-2), was capable of generating LAK activity when TCGF was used as the source of lymphokine. LAK cells induced by TCGF from the 211-depleted population lysed a fresh sarcoma and an NK-resistant cultured melanoma tumor target but not the Daudi cell line, which was lysed by rIL-2-induced LAK cells. Lymphoid subpopulations, depleted using NKH1a mAb, behaved similarly, generating high levels of lysis against the two solid tumor targets when cultured with TCGF but not with rIL-2. CD 3-depleted populations showed enrichment for LAK precursors using either rIL-2 or TCGF. These results indicate that while rIL-2-induced LAK precursors cannot be separated from cells with NK activity, TCGF-induced LAK cells can be generated from populations of peripheral blood mononuclear cells without NK activity.     

Defective B cell clonal regulation and autoantibody production in New Zealand black mice

By using the splenic fragment assay in a KLH-primed host, we have evaluated the clonal anergy model of tolerance in DBA/2 and spontaneously autoimmune NZB mice. Unlike immature B cells from DBA/2 mice (which are tolerized by encounter with TNP-OVA), SIg- B cells from NZB mice respond to TNP-KLH with equal precursor frequency in TNP-OVA-tolerized or control fragments. In additional experiments, SIg- bone marrow or mature spleen cells of DBA/2 or NZB origin were adoptively transferred into irradiated (DBA/2 X NZB) F1 X xid hosts, and host-derived splenic fragments were stimulated in vitro with LPS and growth factors. These experiments revealed a substantial anti-ssDNA precursor frequency in NZB marrow and spleen (2.5 and 5.1, respectively, per 10(7) transferred cells). In DBA/2 SIg- marrow cells, there was an anti-ssDNA precursor frequency of 1.3 to 3.5/10(7) transferred cells; however, anti-ssDNA-producing clones were reduced in fragments derived from recipients of DBA/2 as compared with NZB spleen cells (0.2 to 1.9/10(7) transferred cells). By using a replica plate technique, we evaluated fragments from recipients of DBA/2 SIg- marrow cells or mature spleen cells for anti-TNP reactivity. In fragments derived from recipients of DBA/2 SIg- marrow cells, 92% of anti-TNP-producing fragments also bound ssDNA. In fragments derived from recipients of DBA/2 spleen cells, only 43% of anti-TNP-producing fragments also bound ssDNA. Our findings document that NZB marrow-derived immature B cells abnormally resist tolerance induction, and that clonal anergy/selection operates in directing the B cell repertoire away from autoantibody formation.     

Defective isotype-specific regulation of IgA anti-erythrocyte autoantibody-forming cells in NZB mice

B cell hyperactivity characterizes many autoimmune diseases. In NZB mice this is manifested by a variety of immunologic aberrations, including increased B cell proliferation and hyper IgM and IgA secretion in vitro. Recent studies have shown that IgA secretion can be suppressed or enhanced in an isotype-specific manner by a soluble factor(s), called IgA-binding factor (IgABF), produced by IgA FcR-bearing T cells. We now show that T cells from young NZB mice, cultured with high concentrations of IgA, produce an IgABF that has aberrant biologic activity when compared to IgABF produced from IgA FcR+ T cells of BALB/c mice. Although BALB/c IgABF normally suppresses proliferation and secretion by IgA-producing B cells, neither proliferation nor IgA secretion from normal murine IgA-B cells is suppressed by NZB IgABF. In fact, IgA secretion is significantly enhanced by NZB IgABF. We also present the first evidence of IgA anti-mouse erythrocyte (anti-MRBC) autoantibody-forming cells present in the spleens of NZB mice. Whereas BALB/c IgABF suppresses the in vitro generation of IgA anti-MRBC autoantibody-forming cells by NZB spleen cells, NZB IgABF enhances this response. Of particular interest is the development of IgA anti-MRBC autoantibody-forming cells in cultures of spleen cells from nonautoimmune BALB/c mice in the presence of NZB IgABF. These studies suggest that isotype-specific T cells factors might play an important role in the development of autoantibody-forming cells.     

Cell cycle analysis of lymphocyte activation in normal and autoimmune strains of mice

The spontaneous spleen cell proliferation and the proliferation induced by in vivo or in vitro stimulation with such polyclonal B cell activators (PBA) as LPS, poly rI.rC, and anti-mu were studied in normal and autoimmune mice. The various murine models of autoimmunity differ in the level of naturally occurring splenic cellular hyperactivity as well as in the ability of their spleen cells to be further stimulated in vitro by polyclonal stimulators. Both the NZB strain and the MRL/Ipr strain had markedly increased numbers and percentages of spontaneously proliferating spleen cells, whereas the BXSB strain did not. Nonautoimmune strains were found to have very small numbers of activated cells in the spleen. However, such normal strains could be induced in vivo to mimic the natural splenic hyperactivity observed in older NZB and MRL/Ipr autoimmune strains by the injection of polyclonal B lymphocyte stimulators. In contrast, old hyperactive NZB mice were not further induced to undergo proliferation by in vivo administration of such stimulators. Density-separated, T depleted, spleen cells of normal and autoimmune mice were stimulated in vitro with PBA in 48-hr cultures. Cells from old MRL/Ipr and NZB mice were abnormal in both the anti-mu response and the LPS response; BXSB mice had normal anti-mu responses. These studies suggest that there is no prerequisite for spontaneous splenic hyperactivity in the development of autoimmunity. In addition, different PBA stimulate separate subsets of B cells that differ in their state of activation in the various autoimmune strains. Finally, different B cell subsets appear to be abnormal in different types of autoimmune mice.     

The production of T-cell growth factor (TCGF) in vivo in sheep

Lymph and supernatants derived from efferent lymphocytes leaving the popliteal lymph nodes of sheep responding to human red cells or dinitrophenylated bovine serum albumin were examined for the presence of T-cell growth factor (TCGF). Efferent cells from normal sheep, but not from antigen-stimulated sheep, were found to release low levels of TCGF when incubated in medium for 12 hr in the absence of any exogenous stimulus. High levels of TCGF were found in normal lymph and also in immune lymph collected from sheep during the first 6 hr of immune responses. There were no detectable levels of TCGF in lymph collected later in the response. The lymphokine appeared to be a single molecular species of 10,000–20,000 molecular weight as assessed by exclusion chromatography. Efferent cells expressing receptors for TCGF were found in efferent lymph during the first 12 hr of the response. The results demonstrate for the first time that TCGF is produced in vivo and that asynchrony exists between TCGF production and expression of receptors for TCGF on efferent cells released by the stimulated node. Based on the known kinetics of previously reported synergistic factors, mitogenic factors, and T-cell-replacing factors in sheep efferent lymph and their physical characteristics it was concluded that the TCGF detected in lymph is distinct from these factors.     

Selective in vivo antitumor effects of monoclonal anti-I-A antibody on B cell lymphoma

In a study of the biologic consequences of using monoclonal antibodies (mAb) with specificity for I-A for the elimination of an I-A-bearing B cell lymphoma, it was found that, despite the presence of I-A on a number of normal cell types and the propensity of anti-I-A to induce modulation of I-A and I-E on normal cells in vivo, a substantial effect on lymphoma growth could be measured in mAb-treated hosts. Unlike I-A on normal cells, tumor I-A failed to modulate in vivo, and 50% of animals could be cured of lymphoma by multiple doses of anti-I-A mAb. With a sensitive spleen tumor colonization assay, it was shown that neither T lymphocytes nor natural killer cells were involved in tumor elimination by anti-I-A mAb. In addition, C3 depletion only minimally affected the ability of anti-I-A to inhibit tumor growth, suggesting that complement-dependent lysis of tumor cells was not a major mechanism. Spleen cells from long term survivors of tumor challenge and mAb treatment functioned normally as antigen-presenting cells and in the recognition of alloantigens, and serum Ig levels were somewhat higher than in untreated mice; thus, such therapy can be carried out without compromising the immune reactivity of long term survivors.     

Specific antigen-binding and antibody-secreting lymphocytes associated with the erythrocyte autoantibody responses of NZB and genetically unrelated mice.

The receptor characteristics as well as incidence of antigen-binding lymphocytes (ABL) or B and T cell classes with membrane receptors specific for the exposed (X) and cryptic (HB) murine erythrocyte autoantigens were examined in NZB and nine control strains of mice. Whereas only NZB and NZB hybrid mice synthesize anti-X autoantibody pathogenetically implicated in the genetically determined autoimmune hemolytic anemia, the NZB as well as control strains synthesize the ubiquitous anti-HB anti-erythrocyte autoantibody. By utilizing immunocytoadherence assays, maximum numbers of specific ABL of both B and T lymphocyte classes were optimally demonstrated at erythrocyte:lymphocyte ratios of 20:1 and after lymphocyte fixation at 56 degrees C for 20 min. Surface membrane receptor specificity was established by inhibition with semi-purified soluble X or HB autoantigen. Inhibition of immunocyto-adherence with class specific antisera to mouse immuno-globulins demonstrated that the receptors on both B and T cells were of IgM class. Specific receptors regenerated in vitro after trypsinization which excluded the role of cytophilic antibody in the immunocytoadherence reactions. B lymphocyte ABL reactive with the X autoantigen were demonstrable in NZB, NZB hybrid, and control mice. Only in NZB and NZB hybrid mice, strains that uniformly synthesize anti-X autoantibody, were X ABL of T lymphocyte class demonstrated. The presence and incidence of T lymphocyte X ABL is compatible with the expression of a single dominant gene carried by the NAB strain. The incidence of B lymphocyte X ABL increased with age, suggesting proliferation of this cell population. HB ABL of both B and T lymphocyte classes were observed in all strains, concordant with the ubiquitous presence of humoral anti-HB autoantibodies. Differentiation of precursor B cells are evaluated by PFC assay of cells secreting specific autoantibodies. Anti-X PFC were observed only in NZB and NZB hybrid mice; and the observed frequency suggested that less than 3.5% of the specific ABL were differentiated for the secretion of anti-X autoantibody. Anti-HB PFC were observed in all strains and represented as high as 11.8% of specific ABL. Genetic determination of the anti-X anti-erythrocyte autoantibody response does not prescribe the presence of precursors of the antibody-forming cell, but rather appears to influence regulation of the differentiation of these cells. These data suggest that circumvention of immunologic tolerance to this specific erythrocyte autoantigen may occur at the level of the T lymphocyte; or alternatively, that T lymphocytes as well as B lymphocytes, are induced to proliferate and differentiate in the NZB strain.     

Expression of Lyt-1 by a subset of B lymphocytes

Using two-color flow cytometry and multiparameter data analysis, we have shown that the IgM bright, large subset of mouse splenic B lymphocytes express Lyt-1. This is not due to B cell uptake of immune complexes of Lyt-1 and antibody from T cells. The IgM bright cells of autoimmune NZB mice express more Lyt-1 than normal controls. This is because IgM containing plasmablasts, which are greatly increased in NZB spleens, are Lyt-1+. NZB spleen also contains more cells that are Lyt-1+ (but perhaps Lyt-1.2-), Thy-1.2 dull, and smaller in size than cells in normal mice. Thus, Lyt-1 is common to the T and B cell precursor or is induced independently during the ontogeny of T and at least one subset of B cells. We suggest that it be called Lyt-1.     

Developmental abnormalities of terminal deoxynucleotidyl transferase positive bone marrow cells and thymocytes in New Zealand mice: effects of prostaglandin E1

The enzyme TdT was used as a marker with which to study the ontogeny of primitive lymphopoietic cells in NZ strain mice. A marked accumulation of abnormally large, rapidly proliferating TdT+ cells was seen in the subcapsular region of the thymus cortex in the NZB and NZB/W mice. This abnormal accumulation of TdT+ thymocytes was most pronounced in the NZB/W hybrid and persisted for at least the first 16 wk of life. In addition, significantly elevated percentages of TdT+ bone marrow cells (presumptive prothymocytes) were present in NZB, NZW, and NZB/W mice between 1 and 4 wk of age, with the highest mean peak levels occurring in the NZB strain. Treatment of both normal and adrenalectomized BALB/c and NZB/W mice with pharmacologic doses (7 to 10 mg/kg) of PGE1 caused a marked, dose-dependent decrease in thymus weight and thymus cell number within 12 to 18 hr. Histologic and cell separation studies showed that this was due to the selective depletion of PNA+ TdT+ cortical thymocytes. Similarly, PGE1 caused a reversible, dose-dependent decrease in the percentage of TdT+ bone marrow cells. In contrast, PGF2 alpha, which is not therapeutically active against autoimmunity in NZB/W mice, had no detectable effect on TdT+ bone marrow cells or thymocytes in BALB/c or NZB/W mice. These results directly document the existence of abnormalities in the development of lymphopoietic precursor cells in the bone marrow and thymus cortex of NZ strain mice prior to the onset of autoimmune phenomena. The results also raise the possibility that the therapeutic efficacy of exogenous PGE1 in autoimmune NZ strain mice may be related, at least in part, to its ability to rectify the abnormal development of these early lymphoid cells.     

Changes in the compositions of the null cell compartment with murine autoimmunity

The subpopulations that comprise the null cell compartment were examined sequentially in various strains of autoimmune-prone mice. Different patterns emerged that were consistent within strains but differed from strain to strain. Abnormalities appear earlier in life in short-lived mice, such as male BXSB and MRL/1 mice, than in relatively long-lived strains, such as female BXSB and NZB mice. The accumulation of T cells in MRL/1 mice was accompanied by null cell changes that contrasted with those that developed in AKR/J mice after their spleens were infiltrated with leukemic T cells. It would seem that lymphocyte perturbations with murine autoimmunity also involve their precursor cells and that these precursor cell changes vary in different strains, perhaps in relation to different genetic factors.