T-lymphocyte subsets in nude mice with Giardia muris infection

The aim of this study was to compare the relative percentages of T-lymphocyte subsets in athymic (nude) mice and immunocompetent BALB/c mice, with and without Giardia muris infection. Suspension of mononuclear leukocytes from blood, spleen, and Peyer's patches of uninfected mice were incubated with fluorescent monoclonal antibodies (MAbs) directed against mouse T-lymphocytes (anti-Thy-1.2 MAb), T helper/inducer lymphocytes (anti-L3T4 MAb), or T suppressor/cytotoxic lymphocytes (anti-Ly-2 MAb), and examined by fluorescence microscopy to quantify each of these cell populations. While the percentages of Thy-1.2+, L3T4+, and Ly-2+ lymphocytes are all reduced in nude mice, L3T4+ lymphocytes were found to be especially depleted, resulting in a reversed L3T4+/Ly-2+ ratio (less than 1) in all of the nude mouse tissues examined. BALB/c and nude mouse Peyer's patch T-cell subsets were quantified at various times during enteric Giardia muris infection. Unlike immunocompetent BALB/c mice, nude mice have an impaired ability to clear this infection. It was found that clearance of G. muris infection is associated with a Peyer's patch L3T4+/Ly-2+ ratio of greater than or equal to 2, and that this infection does not alter the percentages of Peyer's patch Thy-1.2+, L3T4+, or Ly-2+ lymphocytes in BALB/c mice or nude mice. The data obtained in the present work and in other studies suggest that the impaired capacity of nude mice to clear G. muris infection results from deficiency of L3T4+ lymphocytes.     

Selective production of interleukin 3 (IL3) and granulocyte-macrophage colony-stimulating factor (GM-CSF) in vitro by murine L3T4+ T cells: lack of spontaneous IL3 and GM-CSF production by Ly-2-/L3T4- lpr subset

Murine spleen and lymph node L3T4+ T cells were found to spontaneously produce high levels of interleukin 3 (IL3) and granulocyte-macrophage colony-stimulating factor (GM-CSF) in cultures containing 10% fetal calf serum (FCS) in the absence of other stimulation. The IL3 and GM-CSF activities in culture supernatants peake between the fifth and seventh day of culture. The specificity of the bioassays was attested by the use of rabbit anti-IL3 and anti-GM-CSF antibodies, as well as by the detection of a maximal accumulation of IL3 and GM-CSF mRNA on the fourth day. In contrast, no significant activities of IL2, IL4 or interferon-gamma were detected in these culture supernatants. The markedly limited production of IL3 and GM-CSF in cultures performed in 1% autologous normal mouse serum and the inhibitory effect of anti-Ia or anti-L3T4 monoclonal antibody strongly suggest that the selective production of most, if not all IL3 and GM-CSF by L3T4+ T cells is a result of activation of L3T4+ T cells by fetal calf serum. All the strains of mice tested except athymic nude mice produced substantial amounts of IL3 and GM-CSF during the culture. This is in contrast to a previous report (Palacios, Eur. J. Immunol. 1984. 14: 599), indicating that only spleen cells of the MRL strain homozygous for the lpr gene spontaneously release IL3 in cultures. We found that spleen and lymph node cells from MRL/MpJ-lpr/lpr or C57BL/6J-lpr/lpr mice released, in fact, much less IL3 and GM-CSF in cultures. This was, however, due to the high proportion of the peculiar lpr Ly-2-/L3T4-T cells in spleen and lymph nodes, since after depletion of this lpr T cell subset, lymph node cells from C57BL/6J-lpr/lpr mice produced IL3 and GM-CSF at levels comparable to those in C57BL/6J-+/+ mice. These results further support the notion that the lpr Ly-2-/L3T4- T cell subset is immunologically nonfunctional and its accumulation dilutes functional L3T4+ T cells in mice bearing the lpr mutation.     

Administration of recombinant interleukin 2 to mice enhances production of hemopoietic and natural killer cells

Seven days of continuous perfusion of mice with human recombinant interleukin 2 (rIL 2) (approximately 3 X 10(4) U/day) increased the percentage of large mononuclear leukocytes (LML) among bone marrow, spleen, lymph node cells and liver interstitial cells (LIC). An increase in the lymphokine-activated killer (LAK) activity was evident in these organs. The greatest increase in the number of LML and in the LAK activity was observed among the liver interstitial cells (about 500-fold increase). The LML were nonphagocytic, Thy-1+, sIg-, Ly 2+, L3T4- and asialo Gm1+. Perfusion of athymic nude mice, or of thymectomized, irradiated radiation chimera, showed that the Thy-1+, LAK+ LML were the thymus and T lymphocyte-independent progeny of Thy-1- marrow precursors. The LML had no T cell function in a graft-vs.-host reactivity assay, neither did they have an inhibitory effect on T lymphocyte function in vivo. rIL 2 perfusion did not significantly affect the medullary hemopoiesis but did strongly enhance the extramedullary hemopoiesis, particularly within the interstice of the liver: the number of erythroid and myeloid cell was increased as well as the number of colony-forming units per spleen and colony-forming units per culture for various lineages (20-50-fold increment). These results show that in vivo, rIL 2 has a global enhancing effect on hemopoiesis together with a more selective influence on the production of LML.     

Systemic administration of IL-2 induces lymphokine-activated killer (LAK) cells capable of killing macrophages in various tissues.

Murine lymphokine-activated killer (LAK) cells induced by systemic high-dose recombinant human interleukin 2 (IL-2) administration lysed fresh syngeneic peritoneal macrophages (M phi). LAK cells lysed resident peritoneal M phi and M phi activated in vivo with thioglycollate (TG), Corynebacterium parvum (C. parvum), or Bacillus Calmette-Guérin (BCG). The induction of anti-M phi cytolytic activity was seen in the spleen, liver, lung, lymph nodes and peritoneal cavity, but was not observed in the thymus. Fluorescence analysis revealed that the majority of infiltrated cells in the peritoneal cavity of IL-2-administered mice were Thy-1+, asialo GM1+, L3T4-, Ly2-. Surface marker analysis on peritoneal exudate cells (PEC) from IL-2-administered mice with depletion techniques using antibody (Ab) and complement (C) indicated that Thy-1+, asialo GM1+, L3T4-, Ly 2- cells were responsible for anti-M phi lysis. These studies indicate that the in vivo administration of IL-2 induces LAK cells capable of killing M phi in various tissues.     

Development of autoreactive L3T4+ T cells from double-negative (L3T4-/Ly-2-) Thy-1+ spleen cells of normal mice

Thy-1+/L3T4-/Ly-2- spleen cells were purified from normal C57BL/6 (B6) and C,B-17 mice. Cells within this subset expressed the T cell receptor (TcR) for antigen: the majority of cells in this subset were CD3+; a fraction of the cells was stained with the monoclonal antibody (mAb) F23.1; and the TcR molecule was immunoprecipitable with mAb F23.1 from cells within this subset. In limiting dilution analyses, about 1/30 cells within this subset were growth inducible in vitro by stimulation with phorbol myristate acetate (PMA) plus ionomycin; conditioned media containing interleukin (IL) 1, IL2, IL3 or IL4 activity neither triggered nor promoted in vitro growth of these cells. The in vitro generated T cells displayed the Thy-1+/L3T4+/Ly-2- surface phenotype and were self-reactive, i.e., proliferated preferentially in response to syngeneic stimulator cells, and secreted IL2 and IL3 only in response to syngeneic but not allogeneic stimulator cells. The proliferative response of these cells to syngeneic stimulator cells was blocked by anti-self Ia mAb. This autoreactive helper T cell subset was not inducible in purified Thy-1+ spleen cell subsets from athymic nude mice or scid mice. Autoreactive helper T cells did not express detectable levels of the IL2 receptor (IL2R), and their proliferative response was not blocked by anti-IL2R mAb. From PMA plus ionomycin-stimulated double-negative Thy-1+ spleen cells, 14 T cell clones were established in long-term culture which displayed the CD3+CD4+CD8- surface phenotype and were self-reactive.     

CD4-/CD8-T cells: amplification in spleens of mice following in vivo treatment with monoclonal antibody anti-L3T4

Amplification of L3T4-/Ly-2-(CD 4-/CD 8-) T cells following in vivo administration of anti-L3T4 monoclonal antibody was examined in the spleen of mice by flow cytometry and immunohistochemistry. BALB/c mice were given 4-7 weekly injections of either anti-L3T4 (1 mg/week) or phosphate-buffered saline (control group), and dispersed spleen cells and tissue sections analyzed for the presence of Thy-1.2+, L3T4+, or Ly-2+ cells, and for the absence of both L3T4 and Ly-2 on Thy-1.2+ cells. Prior to treatment, L3T4+ and Ly-2+ cells accounted for virtually all Thy-1.2+ cells in approximately a 2:1 ratio. Following anti-L3T4 treatment, L3T4+ cells were depleted, and Ly-2+ cells accounted for about 2/3 of the Thy-1.2+ cells. A population of L3T4-/Ly-2- T cells was generated that accounted for 20-30% of the Thy-1.2+ cells, accounted for most of the Thy-1.2+ cells in red pulp, and was also present among the predominant Ly-2+ cells in periarteriolar sheaths.     

Analysis of CD3 and antigen receptor expression on T cell subpopulations of aged athymic mice

The expression of the T cell antigen receptor on subpopulations of extrathymically generated T cells from athymic mice was investigated and compared to antigen receptor expression in normal mice. To this end, spleen and lymph node cells from 18 individual athymic BALB/c nu/nu mice between 6 and 12 months of age and from normal controls were enriched for T cells by nylon wool filtration. Expression of the following cell surface markers was analyzed by two-color flow cytometry: Thy-1, CD4, CD8, V beta 8 and CD3. The distribution of subpopulations as defined by these markers varied much more among athymic than among normal mice. Some recurrent patterns did, however, occur that may be characteristic of the extrathymic pathway of T cell differentiation in nu/nu mice. Among Thy-1.2+ cells, CD8+ cells predominated over CD4+ cells. No CD4+8+ "double positive" cells were found, but CD4-8- "double negative" cell constituted 16% on average. All nu/nu nylon wool-nonadherent cells expressing Thy-1 at a normal level also expressed CD3, whereas Thy-1low and Thy-1- cells were CD3-. The fraction of V beta 8 T cells among the CD4+ and CD8+ subsets was near to normal in the majority of these animals. Most interestingly, the density of V beta 8 and CD3 expression was lower in athymic than in euthymic animals. This level of T cell antigen receptor expression was, however, higher than on immature CD4+8+ thymocytes. A fraction of the nude T cells presently characterized responded with proliferation to both anti-T cell receptor V beta 8 monoclonal antibody and to concanavalin A. Despite their apparently normal phenotype (with the exception of reduced T cell receptor expression), this response was, however, 4 to 10 times smaller than that of normal control cells. The presently described Thy-1+ T cell receptor intermediate cells may either be a(n) aberrant lineage(s) only generated extrathymically, or represent the accumulation of an immature intermediate stage of normal (i.e. thymic) T cell differentiation.     

The expression of murine alloantigens on blood lymphocytes

Single- and two-colour immunofluorescence was used to analyse and compare the expression of 12 antigens on the surface of Ig- mouse blood lymphocytes (BL) and Ig- lymph node (LN) cells. Studies in different strains of mice showed that: (i) there were fewer Thy-1+, Ly 1+, L3T4+ cells in BL compared to LN; (ii) Ly 2+ BL showed a unique fluorescence profile with a temporal variation in antigen density not evident in LN; (iii) Thy-1- Ly 1- cells were more common in BL than LN; (iv) L3T4 and Ly 2 were present on mutually exclusive subpopulations in BL; (v) Ly 6A, (Ly 6.2), Ly 6C (Ly 28.2) Ly 28.6C and Ly 12.1 antigenic determinants were expressed on the same proportion of BL and LN cells and to the same level; (vi) Ly 24 (Pgp-1) was the only alloantigen examined where the number of positive cells was increased in BL (65%) compared to LN (40%); (vii) Ly 5 and Ly 15 (LFA-1) showed significant differences in antigen density distribution between BL and LN; (viii) Ly 21.2 was similar to Ly 15.2 expression; (ix) 20% of Ig-LN cells were Ia+, but Ia was absent from Ig-BL. Thus, BL differ in antigen distribution and density from lymphocytes in LN and other tissues and should be considered as a unique population of lymphocytes.     

MHC- and Igh-unrestricted interaction between L3T4+, Lyt-2- Ts inducer cells and L3T4-, Lyt-2+ Ts effector cells is required for T cell-dependent suppression of DTH to histocompatibility antigens

This paper describes the characteristics of T suppressor inducer (Ts ind) cells which can interact with T suppressor effector (Ts eff) cells and thereby can account for suppression of delayed-type hypersensitivity (DTH) to alloantigens. Adoptive transfer of spleen cells from mice intravenously (i.v.) injected with allogeneic spleen cells one day earlier induced an antigen-specific state of suppression in the recipients. This became apparent when DTH was induced by subcutaneous (s.c.) immunization of the recipients three days after transfer. The induction of suppression after adoptive transfer of spleen cells required Thy-1+, L3T4+, Lyt-1+2- cells. These cells that by themselves did not exert a suppressive effect induced a state of suppression in recipient mice by activation of recipient-type Ts eff cells. Therefore, the former cell type was classified as Ts ind cell. When athymic nude mice were used as recipients, Lyt-2+ precursors of Ts eff cells had to be transferred together with the Ts ind cells to induce a state of suppression in these mice. The Ts ind cells could activate Ts eff cells in MHC- and Igh-incompatible recipients. The results are discussed in relation to previously described immunoregulatory T cell pathways.     

Characterization of V beta-bearing cells in athymic (nu/nu) mice suggests an extrathymic pathway for T cell differentiation

In the present article, the expression of the T cell receptor (TcR) beta chain and other T cell molecules was evaluated in surface immunoglobulin-negative spleen cell populations of young and old BALB/c and C57BL/6 nude mice, using a panel of monoclonal antibodies. The results obtained show that in young nude mice, most Thy-1high cells do not express other T cell markers. These mice have, however, a sizable population of Thy-1low cells with the same phenotype of alpha/beta+, CD4-CD8- thymocytes or MRL/lpr peripheral T cells, expressing predominantly genes of the V beta 8 family. The evolution of alpha/beta+ cells in aging nudes is strongly suggestive of an extrathymic pathway of differentiation of these cells since (a) the acquisition of high density TcR and CD3, as well as Thy-1 or CD4CD8 antigens at the cell surface of nude V beta+ T cells is not simultaneous; (b) alpha/beta+ cells in nude mice co-express other T cell markers at random and, even in old mice, they never completely resemble to the predominant high Thy-1+ CD3+ TcR alpha/beta+, CD4+CD8+ cells of euthymic controls; and (c) BALB/c nude T cells express V beta 11 genes, that are deleted in euthymic BALB/c mice. This latter finding may also indicate differences in the mechanisms of selection of T cells specificities in the thymus vs. the peripheral pools.     

Phenotype of intraepithelial lymphocytes in euthymic and athymic mice: implications for differentiation of cells bearing a CD3-associated gamma delta T cell receptor

This study was carried out to determine the exact phenotype of intraepithelial lymphocytes (IEL) in euthymic and athymic nude mice. The phenotype of IEL in euthymic and athymic mice is mainly CD3+CD8+. However, based on Thy-1- and CD3-associated receptor expression we can subdivide the CD3CD8 population into different subpopulations in euthymic and athymic mice. In euthymic and athymic mice several CD3CD8 populations can be defined. One population expressing Thy-1 and the T cell receptor (TcR) alpha beta is absent in athymic mice. Two other CD3+CD8+ populations can be detected in euthymic and athymic mice. Based on Northern blot and flow cytometric analysis we have to conclude that these populations express the CD3-associated TcR gamma delta. One of the TcR gamma delta-expressing populations also expresses Thy-1 at low surface density. This is in contrast to the CD3CD8 population expressing the TcR alpha beta, which expresses Thy-1 at high surface density. There are also, however, especially in athymic nude mice, significant numbers of CD3-CD8+ cells present with the same localization as IEL. The function of these cells is yet unknown. Using a probe for the delta chain we have shown that IEL preferentially express 2-kb mRNA, while nearly no delta chain 1.7-kb mRNA is expressed by these cells. This is in contrast to delta mRNA in thymocytes. Equal quantities of the 1.7- and 2.0-kb delta chain mRNA species were found in RNA isolated from thymocytes. The results imply that CD3+CD8+ intestinal IEL expressing the CD3-associated TcR gamma delta can differentiate in absence of the thymus and represent a thymus-independent lineage of cells bearing this receptor.     

CD4+CD8+ thymocytes develop into CD4 or CD8 single-positive cells in athymic nude mice

A differentiation pathway from CD4+CD8+ cells to CD4+CD8- or CD4-CD8+ cells was investigated in athymic nude mice. Using fluorescence-activated cell sorter, CD4+CD8+ cells were sorted out from AKR thymocytes (H-2k, Thy-1.1) stained with two monoclonal antibodies against CD4 and CD8 (anti-L3T4 and anti-Ly-2). These CD4+CD8+ AKR thymocytes were injected i.v. into CBA or C3H nude mice (H-2k, Thy-1.2) which had received 650 rads and had been reconstituted with syngeneic nude bone marrow cells. The lymph node cells of the nude recipients at 4 wks post-thymocyte transfer were shown to contain 50% AKR-derived Thy-1.1+ cells. The majority of the Thy-1.1+ cells were found to express either CD4 or CD8 alone but not to express both CD4 and CD8. These findings indicate that CD4+CD8+ thymocytes can develop into CD4+CD8- and CD4-CD8+ single-positive cells in extrathymic tissues.     

Contact sensitization to oxazolone: involvement of both interferon-gamma and interleukin-4 in oxazolone-specific Ig and T-cell responses.

The synthesis and role of several lymphokines were examined during contact sensitization to oxazolone (OX). Application of OX to the skin of mice increased the delayed-type hypersensitivity (DTH) response to challenge, serum titres of OX-specific IgG1 and IgG2a, and draining lymph node cell (LNC) numbers. At day 3, LN contained detectable interleukin-4 (IL-4), interferon-gamma (IFN-gamma) and granulocyte-macrophage colony-stimulating factor (GM-CSF) but not IL-2 or IL-3 mRNAs; IL-3 and higher levels of IL-4, IFN-gamma and GM-CSF mRNAs were measured after 24 hr culture with anti-CD3 antibody in OX-primed but not unprimed LNC. As a result of sensitization, LNC secreted IL-3 constitutively and produced elevated levels of IL-2, IL-3, IL-4 and IFN-gamma in response to anti-CD3 antibody; a similar but weaker lymphokine response was recalled by OX-protein conjugate. CD4+ cells were the major source of the anti-CD3-induced lymphokines except IFN-gamma, which was derived mainly from CD8+ cells. Since both IL-4 and IFN-gamma were synthesized by OX-primed LNC in vivo and in vitro, their role was investigated by administering anti-lymphokine antibodies at the time of sensitization. Anti-IL-4 treatment reduced OX-specific serum IgG1 titres without affecting IgG2a titres, whereas anti-IFN-gamma treatment reduced IgG2a but not IgG1 titres. Although neither antibody altered DTH responsiveness, anti-IFN-gamma treatment markedly increased IL-4 production by CD4+ LNC and reduced IFN-gamma production in vitro, particularly by CD4+ cells. We conclude that endogenous IL-4 and IFN-gamma reciprocally influence the isotype of the Ig response to OX and that IFN-gamma also affects the relative levels of IL-4 and IFN-gamma synthesis by CD4+ LNC.     

Sequential activity of gamma-delta T-cell receptor bearing lymphocytes, specific T-cell factors, and alpha-beta T-cell receptor bearing T-cells: a hypothesis

The cell-mediated immune response against cell-bound antigens are biphasic responses. The 'classical' components of cell-mediated immunity such as delayed type hypersensitivity (DTH) and cytotoxic T-cells, are preceded by antigen-specific T-cell factor production. These antigen-specific T-cell factors can be detected in the serum 1-2 days after immunization, which suggests that these antigen-specific T-cell factors play an important role in the initiation of cell-mediated immune responses. Factor-producing lymphocytes can be detected already 1 day after immunization at the site of the antigen challenge, and at first 4-5 days after immunization in the peripheral lymphoid organs. The phenotype of these factor-producing lymphocytes is Thy-1+, CD3+, L3T4 (CD4)-, Lyt2 (CD8)-, whereas the T-lymphocytes inducing the DTH response are Thy 1+, CD3+, L3T4 (CD4)+, Lyt2 (CD8)-. This suggests that these factor-producing lymphocytes are gamma-delta bearing T-lymphocytes. gamma-delta TCR bearing T-cells can develop independently of the thymus, and are present in athymic nude mice. Immunization of athymic (nude) mice induces antigen-specific T-cell factor production as well. This suggests that the gamma-delta bearing T lymphocytes present in nude mice can react to cell-bound antigens and produce these factors.     

Dynamics of T cells of L3T4 and Ly 2 phenotype within granulomas in murine listeriosis.

Monoclonal antibodies anti-Ly 1, anti-Ly 2 and GK1.5 were applied to determine phenotypes of T cells within granulomas formed as a result of infection of mice with the facultative intracellular bacterium Listeria monocytogenes. Early in granuloma formation, equal numbers of Ly 1+, Ly 2+ and L3T4+ cells were found, T cells of different phenotypes being evenly distributed over the lesions. In mature granulomas, numbers of Ly 1+ and L3T4+ cells about doubled as compared to incipient granulomas, Ly 2+ cells, however, remained constant. Whereas Ly 1+ and L3T4+ cells within mature granulomas still were evenly distributed, Ly 2+ cells were predominantly localized in the periphery of the lesions. The data indicate that both, specific Ly 2+ and L3T4+ T cells, display characteristic dynamics within granulomas: Ly 2+ T cells which most likely mature from Ly 1+2+ T cells over time locate to the periphery. Concomitantly, L3T4+ T cells are enriched maintaining their distribution all over the lesions.     

T-cell receptor expression in intestinal intra-epithelial lymphocyte subpopulations of normal and athymic mice.

Intra-epithelial lymphocytes (IEL) in murine small intestine were analysed for the presence of cell-surface antigens and T-cell receptor allotype in normal and athymic BALB/c mice by immunoperoxidase histochemistry on frozen sections and immunofluorescence on isolated IEL. In frozen sections, IEL of normal mice were 97.7% CD45+, 93.5% CD3+, 46.2% Thy-1+, 91.1% CD8+, 10.7% CD4+ and 21.1% KJ16+ (V beta 8.1 and 8.2). FACS analysis of isolated IEL confirmed the level of KJ16 expression and also demonstrated that 25% of IEL were F23.1+ (V beta 8.1-8.3). Immunofluorescent double-staining revealed a skewed distribution of T-cell receptor (TcR) expression on Thy-1+ and Thy-1- IEL. KJ16 and F23.1 were expressed on 25.9% and 32.7% of Thy-1+ IEL, respectively; however, the frequency of V beta 8 expression was diminished on Thy-1- IEL (4.1% KJ16+ and 12.1% F23.1+). IEL are present in athymic mice, but at reduced levels. In frozen sections these cells were 91.9% CD45+, 69.5% CD3+, less than 1% Thy-1+, 83.6% CD8+, less than 1% CD4+ and less than 1% KJ16+. Thus it appears that in normal mice there may be two distinct lineages of IEL, a thymus-dependent Thy-1+ population which utilizes the alpha beta T-cell receptor and a thymus-independent Thy-1- population (represented in athymic mice), which may possibly utilize the alternative gamma delta TcR.     

Active role of T cells in promoting an in vitro autoantibody response to self erythrocytes in NZB mice.

The in vitro anti-self erythrocyte antibody response of NZB spleen cells appears to be influenced directly by T cells. Thy-1+, L3T4+ helper T cells are required for: (i) the generation in vitro of MRBC-specific IgM and IgG AFC by spleen cells from 'autoimmune' (9-12-month old) NZB mice and (ii) the generation in vitro of MRBC-specific IgM and IgG AFC by spleen cells depleted of suppressor cells from pre-autoimmune (2-3-months-old) NZB mice which show no clinical signs of an anti-MRBC response. It is evident from the present and previous studies that the anti-MRBC autoantibody response is regulated in pre-autoimmune spleen cell populations by Ly2+ T cells. Ly2-T cells from both pre-autoimmune and autoimmune mice in sufficient numbers can overcome this normal regulation and promote the anti-MRBC response in cultures of unfractionated pre-autoimmune spleen cells. Ly2- T cells isolated from autoimmune NZB mice were consistently more active in this than the Ly2- T cells isolated from pre-autoimmune mice, suggesting an enrichment of MRBC-reactive Ly2- T cells in autoimmune NZB mice. The Ly2- T cells from autoimmune NZB mice greatly enhance the autoimmune anti-MRBC response relative to a modest enhancement of the response to a foreign antigen, SRBC, produced by the same cells. These data indicate that T cells play an important role both in supporting the autoantibody response to MRBC and in disrupting tolerance, leading to autoimmunity in NZB mice.     

Analysis of splenic lymphocytes with high electrophoretic mobility in adult and aged nude mice

Electrophoretic mobility (EPM) and surface markers of splenic lymphocytes in adult (8 weeks old) and aged (over 1 year old) nude mice were investigated. Splenic lymphocytes in nude mice showed a bimodal pattern consisting of low mobility lymphocytes (LML) corresponding to B cells and high mobility lymphocytes (HML). The HML of nude mice showed the following immunological characteristics: (1) surface Ig- cells; (2) asialo GM1+ cells; (3) an increase in natural killer (NK) activity after depletion of B cells; (4) abrogation of the HML peak and NK activity after treatment with anti-asialo GM1 and complement. These findings suggested that HML in nude mice were NK cells. The mobility of NK cells was slightly lower than that of T cells in normal mice, although their histograms greatly overlapped each other. In the spleen cells of nude mice, there was a significant increase in the numbers of Thy-1+ cells and a decrease in the intensity of asialo GM1 antigen as a function of age. The surface markers of HML were Thy-1+- asialo GM1++ in adult nude mice, but were Thy-1+ asialo GM1+ in aged nude mice. However, although HML in aged nude mice became Thy-1+, these had almost the same EPM as those in adult nude mice.     

Thymus-dependent modulation of Ly49 inhibitory receptor expression on NK1.1+gamma/delta T cells

Major histocompatibility complex (MHC) class I-specific inhibitory receptors are expressed not only on natural killer (NK) cells but also on some subsets of T cells. We here show Ly49 expression on gamma/delta T cells in the thymus and liver of beta2-microglobulin-deficient (beta2m-/-) and C57BL/6 (beta2m+/+) mice. Ly49C/I or Ly49A receptor was expressed on NK1.1+gamma/delta T cells but not on NK1.1-gamma/delta T cells. The numbers of NK1.1+gamma/delta T cells were significantly smaller in beta2m+/+ mice than in beta2m-/- mice with the same H-2b genetic background. Among NK1.1+gamma/delta T cells, the proportions of Ly49C/I+ cells but not of Ly49A+ cells, were decreased in beta2m+/+ mice, suggesting that cognate interaction between Ly49C/I and H-2Kb is involved in the reduction of the number of Ly49C/I+ gamma/delta T cells in beta2m+/+ mice. The frequency of Ly49C/I+ cells in NK1.1+gamma/delta T cells was lower in both lethally irradiated beta2m+/+ mice transplanted with bone marrow (BM) from beta2m-/- mice and lethally irradiated beta2m-/- mice transplanted with BM from beta2m+/+ mice than those in adult thymectomized BM-transplanted chimera mice. These results suggest that reduction of Ly49C/I+ NK1.1+gamma/delta T cells in beta2m+/+ mice is at least partly due to the down-modulation by MHC class I molecules on BM-derived haematopoietic cells or radioresistant cells in the thymus.