Generation of F1 hybrid cytotoxic T lymphocytes specific for self H-2

Reduced alloreactive T-cell activation after alcohol intake is due to impaired monocyte accessory cell function and correlates with elevated IL-10, IL-13, and decreased IFNgamma levels

BACKGROUND

Immunosuppression associated with chronic alcohol use is characterized by reduced antigen-specific T-cell response and impaired delayed type hypersensitivity. Increasing evidence suggests in chronic alcohol consumption models that reduced antigen-specific T-cell proliferation is due to insufficient accessory cell function. Accessory cell function, a critical step in recognition of viral antigens, is reduced in chronic hepatitis C. The severity of hepatitis C is increased by alcohol consumption. Thus, we investigated the effects of alcohol consumption on accessory cell activity of monocytes in supporting alloreactive T-cell proliferation.

METHODS

Alloreactive T-cell proliferation was evaluated in a one-way mixed lymphocyte reaction (MLR). Mononuclear cells were isolated by Ficoll density gradient and monocytes by adherence. Alcohol (0.8 g/kg body weight, an equivalent of approximately three drinks) was given to nonalcohol-consuming individuals and blood samples were collected before, 4 hr, or 18 hr after alcohol consumption. Alcohol in vitro was administered at concentrations of 25-100 mM.

RESULTS

T-cell proliferation in MLR was significantly reduced in the presence of physiologically relevant concentrations of alcohol in vitro (25-100 mM ethanol) (p < 0.05). In vivo alcohol consumption also depressed proliferation in the MLR when stimulator cells were obtained 4 hr after alcohol consumption. MLR was not decreased, however, in the presence of alcohol-exposed responder cells and normal stimulator cells, suggesting that the accessory cell population and not T cells are affected by alcohol. Decreased accessory cell function was further evidenced by reduced superantigen-induced (SEB) but not mitogen-induced (PHA) T-cell proliferation in samples obtained 18 hr after alcohol intake (35% reduction). Reduced accessory cell function was not due to changes in surface expression of monocyte costimulatory molecules (HLA class I, HLA-DR, CD80, CD86, CD40). We found reduced IFNgamma, elevated IL-10, and unchanged IL-4 levels during T-cell proliferation in samples obtained 18 hr after alcohol consumption. Acute alcohol treatment resulted in increased IL-13 in the MLR.

CONCLUSION

These data suggest that even on one occasion moderate alcohol intake can reduce allostimulatory T-cell activation via decreasing accessory cell function. Increased IL-10 and IL-13 plus the reduced IFNgamma production after acute alcohol use are likely to contribute to both the reduced T-cell proliferation and monocyte accessory cell function. These accessory cell mediated defects in T-cell activation may result in impaired antiviral and antitumor immunity after moderate acute alcohol use.

Ethanol impairs major histocompatibility complex (MHC) class II molecule-mediated but not MHC class I molecule-mediated T cell response in alcohol-consuming mice

The goal of this study was to determine whether alcohol affects alloantigen-induced proliferative and cytolytic activity of T cells in mice, and whether the altered immune response was in part due to a defect of IL-2 activity. The ability of spleen cells from individual alcohol-consuming C57BL/6 mice to generate allo-specific mixed lymphocyte response (MLR) and cytotoxic T lymphocyte (CTL) was compared to that of mice fed on an isocaloric maltose diet and regular diet. Allospecific MLR and CTL were generated by sensitizing spleen cells of C57BL/6 mice against spleen cells from BALB/c mice, and the allo-specific CTL activity was determined by the ability of the CTL to kill 51Cr-labeled P815 mastocytoma target cells. Our results showed that the allo-specific MLR of the responder cells from alcohol-consuming mice was significantly reduced (40% reduction, p<0.0 1), and the addition of exogenous interleukin 2 (IL-2) could not reverse the suppression of MLR induced by ethanol. However, our results clearly showed that ethanol has little suppressive effect on allo-reactive CTL of alcohol-consuming mice as compared to the alloreactivity of the control mice (P>0.05). Finally, we also demonstrated that ethanol did not impair the alloantigen-induced IL-2 production in the mixed lymphocyte cultures (P>0.1).

One explanation for F1 antiparent responses

The phenomenon of hybrid resistance, in which F1 offspring reject parental grafts, remains a perplexing problem. Here, Tina Dalianis and Lars Ahrlund-Richter propose that one component of the F1 antiparent response results from competition between the two sets of parentally derived major histocompatibility complex (MHC) molecules for 'promiscuous' peptides. Lack of tolerance in the F1 animal results from insufficient presentation of these peptides on the MHC molecule that has lower affinity for the peptides.

Generation of T cells with lytic specificity for atypical antigens. I. A mitochondrial antigen in the rat

F1 rats primed with normal parental strain lymphocyte populations and restimulated in culture with parental lymphoblasts generate potent cytotoxic T cell responses to unusual antigen systems. Here we describe in the Lewis (L)/DA anti-DA combination an antigen system most likely of mitochondrial origin with the following properties: it is transmitted maternally from DA strain females, inherited in an extra-chromosomal manner, restricted by class I RT1Aa major histocompatibility complex gene products, extinguished on target cells treated with chloramphenicol, and its pattern of expression in different rat strains correlates with restriction fragment-length polymorphisms of mitochondrial DNA. Sequence analysis of the rat ND1 gene indicates that the maternally transferred factor in the rat is not a homologue of the maternally transmitted factor responsible for the mitochondrial antigen in mice. In keeping with its inheritance from DA females, this antigen is present on target cells from (DA female x L male)F1 donors and all other F1 combinations derived from DA female parents, but absent from target cells from some F1 combinations (L/DA and Wistar-Furth [WF]/DA) derived from DA strain males. The presence of this antigen in other F1 combinations (Brown Norway [BN]/DA, August 2880 [AUG]/DA, and PVG/DA) indicates that this mitochondrial antigen system is shared by the DA, BN, and PVG strains, but not by the L and WF strains.

Generation of T cells with lytic specificity for atypical antigens. II. A novel antigen system in the rat dependent on homozygous expression of major histocompatibility complex genes of the class I-like RT1C region

Lymphocytes from parental strain DA rats can induce potent killer cell responses to atypical antigen systems in F1 Lewis (L)/DA and DA/L recipients. Here, we describe an antigen system, H, present on homozygous parental target cells, but not on F1 cells. This antigen system is unusual in several respects: it does not involve class I RT1A gene products usually used by killer cell responses in the rat, it maps to the major histocompatibility complex (MHC) class I-like RT1C region, and it requires homozygous expression of RT1Cav1 alleles. This may be another example, this time involving the RT1C region, of an MHC gene product antigenically altered by an MHC-linked trans-activating modifier gene.

Host H-2 genotype regulates the metastatic ability of H-2-associated variants of B16 melanoma: defense systems screening for absence of self H-2 components by natural killer cells and host-associated homing barrier

The mechanisms of host H-2-associated resistance against metastasis of tumor cells were evaluated in relation to the H-2 phenotype of tumor cells. We used H-2 heterozygous H-2a/b and H-2d/b, and H-2 homozygous H-2b/b hosts, and H-2-associated variant lines of B16 cells (H-2b+, H-2b-). In H-2b/b hosts, H-2+ cells were highly metastatic in vivo, and were resistant to host NK effectors in vitro. Therefore, H-2a/b and H-2d/b hosts showed resistance to metastasis of H-2+ cells and their effectors showed killing activity to these cells in vitro. Though the host resistance was reduced by anti-asialo GM1 serum treatment, these hosts continued to demonstrate a considerable resistance against early survival and metastasis of the B16 cells. To evaluate this natural resistance, aside from the NK system, radiation bone marrow chimeras of F1-parental combinations were used. The data suggest that host MHC-associated resistance involves not only the NK defense system but also the host environmental resistance. Both exert resistance by recognizing the H-2 mismatch in relation to the host.

Resistance to growth of the Moloney lymphoma YAC in semi-syngeneic graft recipients

The growth of the Moloney-virus-induced lymphoma YAC was examined in its strain of origin, A, as well as in 6 AF1 hybrids, ALF1, AB6F1, ACBF1, AABYF1, AACAF1 and AASWF1. "Hybrid resistance", i.e., lower frequency of incidence of tumor takes compared to simultaneous A controls, was observed in all of the tested hybrids. The results with the H-2-congeneic hybrids AABYF1, AACAF1 and AASWF1 indicated that H-2 heterozygosity in itself was sufficient to exhibit hybrid resistance against YAC grafts. The A strain and its H-2 congeneic AABYF1, AACAF1 and AASWF1 hybrids all had similarly low activity in NK assays. Thus, the elevated resistance detected in these H-2 congeneic hybrids did not correlate with NK activity. The rejection capacity of the ALF1, AB6F1 and ACBF1 hybrids correlated to their relatively higher NK activity, when compared to the NK low AABYF1, AACAF1 and AASWF1 hybrids. However, consideration of quantitative differences in between the hybrids which expressed elevated NK activity (i.e., ALF1, AB6F1 and ACBF1) shows that the rejection capacity did not correlate with NK status. The hybrid with the strongest NK effect (ACBF1) was the least resistant to YAC growth (27% palpable tumors), and the hybrid with the weakest NK effect (ALF1) was the most resistant to YAC growth (7.2% palpable tumors).

Regulation of autoimmunity and donor cell engraftment by recipient Lyt-2+ cells during the graft-versus-host reaction

When lymphocytes from DBA/2 mice are transferred to (C57BL X DBA/2)F1 (BDF1) mice, the ensuing graft-vs.-host reaction (GVHR) causes an autoimmune illness resembling human SLE. To examine the role of recipient T cells in this process, BDF1 mice were depleted of L3T4+ or Lyt-2+ cells by thymectomy followed by treatment with mAbs to L3T4 or Lyt-2. This produced sustained depletion of these T cell subsets. Subsequent grafting with parental DBA/2 lymphocytes produced autoimmune disease in mice depleted of L3T4+ cells and controls but not in mice depleted of Lyt-2+ cells. Analysis of blood lymphocytes 4 wk after donor cell transfer demonstrated that BDF1 recipients depleted of Lyt-2+ cells were virtually repopulated with donor T lymphocytes, compared with less than or equal to 35% donor cell engraftment in all other groups. Thus, recipient Lyt-2+ cells influence both host cell engraftment and autoimmunity during the parent-into-F1 GVHR.

Antigen-specific T cell cluster formation on antigen-pulsed macrophage monolayers in mice

We describe the quantitative measurement of antigen-specific clusters formed by antigen-pulsed macrophages and immunized T cells in mice. We have found the peripheral blood T cells show very little non-specific adhesion to macrophages in mice. By using this population of lymphocytes in the peripheral blood as the source of immunized T cells, we could quantitate antigen-specific cluster formation. On OVA-pulsed monolayers of peritoneal exudate macrophages from normal BALB/c mice, syngeneic peripheral blood T cells from donors immunized with the same antigen develop 20-40 clusters per 1,000 macrophages, whereas the same T cells on non-pulsed monolayers develop only 0-5 cluster-like accumulations of cells. On antigen-pulsed monolayers of macrophages from allogeneic (C57BL/6 or A/J) mice, clusters are developed only in the negative range (0-5/1,000 macrophages). Considering the observation by Braendstrup et al, these data seem to suggest that histocompatibility between macrophages and T cells is required to develop antigen-specific T cell clusters on antigen-pulsed macrophage monolayers, and that the genetic restriction of immune responsiveness may be directly expressed in this initial form of cellular interaction between antigen-bearing macrophages and specific T cells.

RISH III. Haplotype-sharing in immune responses

A number of hypotheses have been proposed for the reactivity of lymphocytes with allogeneic tissue. However, these hypotheses have not been generally accepted for they cannot accommodate the observation that lymphocytes from chimeras cooperate with each other. Also, only a few percent of lymphocytes react with allogeneic tissue in rejection reactions.

Rapid changes in specificity within single clones of cytolytic effector cells

We find rapid changes in the specificity of the cytolytic effector cells in a mixed lymphocyte culture. The lysis patterns produced by cytolytic effector cells generated near limiting dilution in murine mixed lymphocyte reactions of three types, F1 anti-parent (F1(A X B) anti-A), allogeneic (C anti-F1(A X B)), and F1 antimodified parent (F1(A X B) anti-A-TNP), were investigated. Cultures were characterized by their ability or inability to lyse a panel of target cells (e.g., A, B, F1). When individual cultures were tested at two different times, changes in lytic pattern were routinely seen, with some patterns reproducibly increasing in frequency and others reproducibly decreasing (e.g., patterns involving lysis of F1 decreased in an F1 anti-A response but increased in a C anti-F1 response). X-linked isoenzyme analysis showed that changes can occur within a single clone of effector cells. These results imply that the T cell specificity repertoire continues to evolve during an ongoing immune response, a conclusion incompatible with clonal selection theory.

Bone marrow graft rejection as a function of antibody-directed natural killer cells

There is conclusive evidence that acute bone marrow transplant rejection in lethally irradiated mice is caused by natural killer (NK) cells. The rejection of marrow allografts is exquisitely specific and is controlled by antigenic determinants encoded in or near the H-2 gene complex. The specificity of in vivo marrow graft rejection contrasts with the in vitro specificity pattern of NK cells in cytotoxicity assays. We therefore examined how NK cells cause H-2-specific marrow graft rejection in vivo. Several experimental approaches are presented that suggest that natural antibody, present in responder strains of mice, specifically directs NK cells in an antibody-dependent cytolytic and/or cytostatic reaction, resulting in marrow graft rejection. The following evidence for this mechanism is documented. The ability to reject a marrow graft can be passively transferred by serum from responder to allogeneic nonresponder mice and the specificity of rejection can be mapped within the H-2 region. Serum-induced marrow graft rejection is abrogated following depletion of immunoglobulin, and the serum of responder mice is able to induce a specific antibody-dependent cytotoxic reaction in vitro.

Immune resistance of semisyngeneic F1 hybrid mice to lymphoma grafts differs from natural hybrid resistance in its genetic pattern

Resistance of semisygeneic F1 hybrid mice immunized three times with irradiated tumor cells was compared to the genetic pattern of natural hybrid resistance to challenge with live tumor cells. Syngeneic mice responded equally well to immunization with all five hemopoietic tumor lines tested as the naturally much more highly resistant F1 hybrids. Natural hybrid resistance was found to be severely reduced by sublethal irradiation with 4 Gy, in contrast to hybrid resistance to parental bone marrow.

Derivation from an alloreactive T-cell line of a clone which cross-reacts with a self H2-E-restricted minor alloantigen

An alloreactive T-helper-cell line [(A.TH X Balb/c) anti-A.TL] was shown to recognize both H2-Ek and H2-Ed. Both proliferation and polyclonal B-cell activation (protein A plaques) were used in the analyses of specificity. On cloning, the H2-Ek/Ed cross-reaction was shown by one clonotype. This cross-reaction is interpreted in light of the P. Matzinger and M.J. Bevan model (Cell. Immunol. 29, 1, 1977) for antigen recognition by T cells. The antigen recognized was a cell surface non-major histocompatibility (MHC) (minor) alloantigen, shared by the DBA and B10 backgrounds, whose recognition was H2-Ed restricted. This clone is therefore both alloreactive and self-MHC (Ed) restricted minor reactive. Other clones from the cell line were either allospecific or autoreactive. It was shown by antibody blocking that the H2-E alpha (Ia7) determinants involved in the cross-reactive and allospecific recognition were not the same. By antibody blocking it was also shown that the antigenic determinant recognized by the autoreactive clone included H2-Ed. The alloreactive cell line therefore contained three H2-E-reactive clonotypes: allo-Ek specific, H2-Ek and DBA/B10 minor plus H2-Ed cross-reactive, and Ed-associated autoreactive.

Natural resistance of lethally irradiated F1 hybrid mice to parental marrow grafts is a function of H-2/Hh-restricted effectors

The natural resistance of F1 hybrid mice against parental bone marrow grafts is thought to be mediated by natural killer (NK)-like effector cells. However, unlike the NK cell activity against a wide range of tumors and normal cells, hybrid resistance is characterized by the immunogenetic specificity controlled by a set of unique noncodominant genes denoted as Hh. Two alternative hypotheses can account for the specificity. Thus, the specificity may reflect either the Hh restriction of effectors or the Hh gene control of mechanisms regulating non-Hh-restricted effector activity. In this study, therefore, we tested the recognition specificity of putative effectors mediating hybrid resistance in lethally irradiated H-2b/d and H-2b/k F1 hybrid mice to the engraftment of parental H-2b bone marrow. As a direct means of defining the effector specificity, rejection of parental bone marrow grafts was subjected to competitive inhibition in situ by irradiated tumor cells. Of the 16 independent lines of lymphoma and other hemopoietic tumor cells tested, the ability to inhibit hybrid resistance was the exclusive property of all tumors derived from mice homozygous for the H-2Db region, regardless of whether the tumor cells were susceptible or resistant to NK cell-mediated cytotoxicity in vitro. Four cell lines heterozygous for the H-2Db were noninhibitory, including one that is susceptible to natural killing. Pretreatment of the F1 hosts with an interferon inducer augmented the resistance with no alteration in the recognition specificity of effector cells. Therefore, natural resistance to parental H-2b bone marrow grafts was mediated by effectors restricted by the H-2Db/Hh-1b gene(s), and not by the nonrestricted NK cells detectable in conventional in vitro assays.

Quantitative variation in la antigen expression plays a central role in immune regulation

The analysis of la antigen function has focused primarily on allelic variants of Ia molecules. In this review Charles Janeway and his colleagues discuss evidence that quantitative rather than qualitative variation in Ia antigen expression had a major role in immunoregulation and immunologically mediated disease.

Involvement of the K and I regions of the H-2 complex in resistance to hemopoietic allografts

Irradiated (H-2b X H-2k)F1 and (H-2b X H-2d)F1 recipients strongly resist the growth of H-2b parental bone marrow cells and do not resist marrow grafts from non-H-2b parents such as C3H and BALB/c. This phenomenon of hybrid resistance has been shown to be under genetic control of the H-2D-linked loci and was interpreted by Cudkowicz (9) as due to the existence of H-2D-linked recessive hemopoietic histocompatibility genes. To check whether the H-2D-linked loci are solely responsible for the fate of bone marrow allografts, we measured the strength of resistance of irradiated (B6 X C3H)F1 and (B6 X BALB/c)F1 recipients toward bone marrow grafts from a set of H-2 recombinant and F1 hybrid donors carrying either the H-2b, H-2d, and H-2k alleles. We found that growth of all H-2b grafts was resisted, although to different degrees. Resistance was minimal when donors shared with the input strain of a corresponding F1 hybrid the H-2K and H-2I regions, or when both F1 donors and F1 recipients formed identical unique hybrid Ia molecules. In addition, H-2b grafts were resisted by congenic, H-2D-identical, H-2K-and H-2I-incompatible recipients. The fate of grafts from H-2Dd donors seemed to depend on the incompatibility of the combinatorial determinant Ia.22. If both donor and recipient expressed such a determinant (either in the cis or in the transposition), or if neither could form such a determinant, grafts were not resisted. The H-2Dk allele is not the main or only factor that confers on the C3H parental bone marrow cells the ability to grow unresisted in (B6 X C3H)F1 recipients. Grafts from congenic C3H.OH donors, carrying the same H-2Dk alleles and differing in the left part of the H-2 complex, were resisted by the F1 recipients. We conclude that both class I (K and D) and class II (I-A and I-E) major histocompatibility complex genes, rather than hypothetical hemopoietic histocompatibility genes control hemopoietic resistance. To reconcile codominant inheritance of classic H-2 antigens with the apparent recessive inheritance of hybrid resistance, we assume that there exist parental determinants that are not formed in some F1 hybrids due to preferential association of either Ia alpha chains with allogeneic beta chains or of class I antigens with allogeneic or hybrid class II restriction elements.

A genetic analysis of natural resistance to nonsyngeneic cells: the role of H-2

The genetic control of natural resistance in vivo to four natural killer (NK) cell-resistant H-2 homozygous lymphoid tumor cell lines was investigated by following the survival and organ distribution of cells prelabeled with radioactive iododeoxyuridine. Backcross mice derived from DBA/2J and CBA/J parents were injected with H-2d tumor cells and tumor cell elimination was lowest in H-2d homozygotes. Natural killer cell activity was also reduced in mice with the H-2d haplotype, but no direct correlation between NK cell levels against YAC-1 or SL2-5 lymphoma cells and natural resistance in vivo was demonstrable. Analysis of 23 BXD recombinant inbred strains indicated that natural resistance to H-2d tumors was restricted to H-2b strains. There was no direct association of NK cell activity with H-2 type in the BXD strains and NK cell levels did not correlate with tumor survival in vivo. By comparing natural resistance to H-2d and H-2b tumors in DBA/2, C57BL/6, B6D2F1, and B10.D2 mice we found that H-2 nonidentity between the tumor and the host, rather than the host H-2 haplotype, determined whether natural resistance occurred. Again, NK cell activity against YAC-1 cells was not predictive of tumor survival in these strains. These results provide genetic evidence that NK cells alone cannot account for natural resistance to H-2 nonidentical cells of hemopoietic origin.

Efficiency of antigen presentation differs in mice differing at the Mls locus

In the mouse, potent primary in vitro proliferation of T cells can be induced by allelic variants of cell-surface glycoproteins, Ia antigens, the genes for which are located in the I region of the major histocompatibility complex (MHC) on chromosome 17. The only other potent primary proliferative response known is induced by mixing MHC-identical lymphocytes from strains that differ at the locus termed Mls (ref. 1) (for mixed lymphocyte stimulating), which has been mapped to chromosome 1. While it is relatively easy to raise antibodies against Ia antigens, and thus determine both their chemical nature and their role in T-cell stimulation, the nature of the product of the Mls locus has remained obscure. It has been proposed that the Mls locus product is a minor antigen recognized in association with self-Ia antigens, a translocated Ia-like element, or a mitogenic molecule found on the surface of antigen presenting cells (APC). Here, we demonstrate that APCs from mice carrying stimulatory Mls locus alleles present antigen more efficiently to cloned, antigen-specific, Ia-restricted T cells than APCs from mice carrying nonstimulating Mls locus alleles. We propose that the Mls locus does not encode a unique cell-surface antigen at all; we suggest instead that the T-cell proliferative response induced by Mls-locus disparate cells reflects recognition of self-Ia molecules on APCs. If our interpretation is correct, it provides further evidence both for the quantitative nature of self tolerance and for the existence of a distinct recognition site for self-Ia molecules on antigen-specific T lymphocytes.

Differentiation from precursors in athymic nude mouse bone marrow of unusual spontaneously cytolytic cells showing anti-self-H-2 specificity and bearing T cell markers

We describe an in vitro limiting dilution culture system that supports growth and differentiation of nylon wool nonadherent bone marrow cells from athymic nude mice. Cells were seeded at low cell numbers (5-120 cells per 20-microliter microculture well) in the absence of added filler or feeder cells but in the presence of conditioned medium. Microwells positive for growth appeared to contain a single clone of cells that adhered together to form a tight cluster referred to here as a colony. A fraction of colonies contained cells that expressed an unusual spontaneous cytolytic activity. They lysed syngeneic or semisyngeneic Con A blast or tumor cell targets but seldom lysed H-2-incompatible Con A blast or tumor target cells, even in a lectin-facilitated assay. A large fraction of colonies contained lymphoid cells that expressed the T cell markers Thy-1 and Lyt-1. Colonies expressing spontaneous cytolytic activity and also containing cells with Thy-1+ and/or Lyt-1+ markers could be grown from nylon wool nonadherent nude marrow cells depleted rigorously by cell sorting of cells expressing either of these markers. Expression of Thy-1 and spontaneous cytolytic activity in a particular colony was significantly correlated. Short-term lines established from cytolytic colonies with T cell markers maintained both characteristics. The cytolytic effector cells observed in these cultures may represent an early stage in the development of the T cell repertoire.

Fate of T-lymphocyte injected into immunodeficient allogeneic nude or semi-allogeneic F1 mice: correlation with manifestations of graft-versus-host reaction

This review emphasizes some of the differences between the fate of allogeneic H2-incompatible T-cells, when injected into immunodeficient, T-depleted mice, or as parental cells injected into F1 hybrids. In both conditions, allogeneic cells are eliminated, a rejection which cannot be predicted from the fate of a skin graft. While in both situations a phase of GVHR is observed, it is of short duration in allogeneic T-B reactions, and it is obvious that the production of allo-antibodies by the host, which is enhanced by the GVHR, is the major mechanism of allogeneic T-cell elimination, resulting in a rapid self-cure of the GVHR. In T-vs-B GVHR, the enhancement of the humoral response is strikingly restricted to the allo-antigens of the T-cells, and correspond therefore to a peculiar form of "allogeneic effect", in fact an "allogeneic suicide" which implies a linked T-B collaboration, while in P-F1 combinations, there is a enhancement of the humoral response to unrelated antigens (i.e. unlinked T-B collaboration or the classical allogeneic effect) and a polyclonal B-cell activation, which can result from the much more protracted course of the GVHR. The parental cells surviving in the spleen of an F1 semi-allogeneic host, undergoing a lethal GVHR were characterized at the clonal level: they were exclusively of the Lyt 2- MLR responder and polyvalent helper variety. This indicates that the Lyt-2- and polyvalent helper subset is selected during an allo-reaction in vivo (either because it is more rapidly replicating and/or less negatively selected by the host resistance) and that it is capable of inflicting a lethal GVHR.

Fetal calf serum-injected F1 mice spontaneously generate specific anti-parental cytotoxic T lymphocytes in in vitro culture

Spleen cells from adult (BALB/c x AKR/J)F1 mice primed in vivo with fetal calf serum (FCS) can spontaneously generate anti-parental AKR/J cytotoxic T cells (CTL) in a 5-day in vitro culture containing 5% FCS. This response is distinguished by the following features: (i) it is anti-parental but not anti-self, and (ii) it has specificity for the Kk parental determinant as shown by mapping studies on a variety of targets and antiserum-blocking experiments. Although specifically elicited by FCS and mediated by FCS-induced T-helper cells, it is ascertained that this cytotoxicity is not directed against Kk components modified by absorbed FCS as shown by cold-target competition studies. Further experiments involved a comparative investigation of the patterns of lysis of allogenically induced CTL, FCS-induced CTL, and natural killer (NK) cytotoxic activities on tumor cell targets. The resistance of BW 5147 tumor targets to NK- and FCS-induced lysis was found to be dramatically overcome by treatment with mitomycin C, and provides circumstantial evidence for a functional relationship between the FCS-induced anti-parental CTL effectors and NK cells based on the observed similarity in lytic patterns of these two effector types. With reference to the work of other authors, the possibility that hybrid resistance and its possible in vitro counterpart, F1 anti-parental CTL cytotoxicity, and NK activity are mediated by similar or common effector mechanisms is discussed.

Hybrid immune response to parental liver tissue grafts

Parental-to-F1-hybrid liver tissue grafts in like-sex donor-recipient combinations survive indefinitely, although several F1 recipients demonstrate an immunological response to the parental graft. Female F1 recipients, particularly those carrying the H-2b haplotype, respond vigorously to male parental liver grafts. However F1 female responses to male parental liver tissue grafts differ substantively from the responses of parental females to syngeneic male grafts. C3H male liver grafts are rejected vigorously by F1 females as long as the F1 carries the H-2b haplotype. These findings support previous reports of strong immunological responses to C3H H-Y antigen in female F1 and C3H.SW animals, a response which is absent in C3H females. Female F1 hybrids carrying the H-2b haplotype do not reject grafts of B10 or B6 male liver as rapidly as do B10 or B6 parental females. This reduced F1 response may be related to the formation of hybrid antigens and consequent alteration of the anti-H-Y response. Alternatively, cells that specifically suppress the anti-H-Y response may be present in F1 hybrids. Factors responsible for suppression appear to be controlled by non-MHC antigens, at least in (C3H X B6 or B10)F1 hybrids.

Thymus independence of hybrid resistance against a panel of T-cell lymphomas of H-2b origin

Adult thymectomy, followed by whole-body irradiation and reconstitution with fetal liver, was performed to study the T-cell dependence of F1 hybrid resistance to a panel of lymphomas of H-2b origin. Previously, the pattern of hybrid resistance against the same lymphomas was found to correlate with the pattern of NK-activity in a spectrum of F1 hybrids (Kiessling et al., 1975). We now show that hybrid resistance against three lymphomas of C57BL/6 origin, P-52-127-166, RBL-5 and EL-4 and against YLD, of C57L origin, is expressed in the absence of thymus. In another series of experiments, the effectors responsible for hybrid resistance to the transplanted lymphoma EL-4 were studied by reconstituting thymectomized and non-thymectomized C57BL mice with syngeneic bone marrow from NK-deficient beige mutant or wild-type C57BL donors. While the recipients of beige bone marrow had a clearly reduced tumor resistance, thymectomy did not decrease resistance further. This study supports the hypothesis that resistance to these lymphomas in F1 hybrids as well as in syngeneic mice is mainly mediated by natural killer cells.

The anti-neoplastic effect of trichinellosis in a syngeneic murine model

C57BL/6 male mice with chronic trichinellosis, and age-matched uninfected control mice, were inoculated with B16 melanoma cells. Tumour development was inhibited in the infected animals. In the infected tumour-bearing mice, the tumor induction intervals were longer and the tumour size was subsequently smaller than in the control mice. Moreover, when the number of tumour cells in the inoculum was less than that required to produce 100% tumour incidence in the uninfected mice (less than 1 x 10(4) cells), significantly more of the mice with an infection of 2 months duration remained tumour-free. These results were significant at the P less than 0.05 level.

Role of H-2 antigens in the host response to methylcholanthrene-induced tumors

H-2 loss variant sublines of a sarcoma (M-AS), induced by methylcholanthrene in an (A x A.SW)F1 mouse, were used to study the role of the MHC products in the recognition of MC-TSTA. The two reciprocal variant sublines (M-A and M-S) were found to express the TSTA of the original tumor as shown by cross-reactions in graft rejection experiments performed in (A x A.SW)F1 mice. In the A/Sn and A.SW mice the presence of the reciprocal parental H-2 antigens on the immunizing cells decreased the response against the tumor antigens. An admixture of lymphocytes derived from hyperimmune mice inhibited the outgrowth of the tumor cells. The growth inhibition was mediated by T cells and was H-2 restricted. Cells derived from hyperimmune immunization but had no effect on the reciprocal variant subline.

Embryo-derived teratocarcinoma. III. Development of tumors from teratocarcinoma-permissive and non-permissive strain embryos transplanted to F1 hybrids

Seven-day-old mouse embryos of two teratocarcinoma-permissive (C3H and BALB/c) and two teratocarcinoma-non-permissive (C57BL/6 and AKR) strains were transplanted to their F1 hybrids to determine the role of the genetic background of the recipient animals in controlling embryo-derived teratocarcinogenesis. The yield of teratocarcinomas in F1 hybrid recipients of embryonic grafts was either identical with the yield in syngeneic recipients or increased or decreased, depending on the strain of the embryo and the F1 hybrid combination. In certain hybrids, the yield of malignant tumors remained the same as in the syngeneic recipients but the F1 hybrids exerted a stimulatory effect on tumor growth and the tumors weighed more than those in syngeneic recipients. A matroclinous effect was also seen in certain hybrids. These data indicate that embryo-derived teratocarcinogenesis in histocompatible F1 mice depends on the genetic background of adult recipients. The teratocarcinogenic potential of non-permissive and permissive strain mouse embryos can be modified by choosing appropriate F1 hybrids for embryonic transplantations.