The role of TDTH and Tc populations in organ graft rejection. I. Functional analysis of graft-infiltrating T cells.

To analyze the role of T cell subpopulations in the rejection of organ allografts, we developed a new model for obtaining large numbers of graft infiltrating cells (GICs). We isolated W3/25+ Th/DTH and OX8+ Ts/c from vascularized, irradiated rat spleen allografts. W3/25+ GICs obtained from spleen allografts transplanted to normal recipients were highly effective in eliciting cardiac allograft rejection when transferred to sublethally irradiated recipients, however, the OX8+ subset was incapable of eliciting rejection. On the other hand, when OX8+ GICs were obtained from spleen allografts transplanted to previously immunized recipients, they were as efficient as the W3/25+ Th/DTH subset in eliciting cardiac allograft destruction. These results indicate that the W3/25+, OX8- T cell is required for the rejection of primary organ allografts, but that the rejection of a secondary allograft by an immune recipient may be mediated, independently, by both W3/25+ and OX8+ cells.

Analysis of the major histocompatibility complex in Syrian hamsters. I. Skin graft rejection, graft-versus-host reactions, mixed lymphocyte reactions, and immune response genes in inbred strains.

Five inbred strains of Syrian hamsters (Mesocricetus auratus) were examined for the presence of disparity at a genetic region similar to the major histocompatibility complex in other species. Vigorous reciprocal alloreactions developed in several strain combinations, which resulted in acute skin graft rejection, strong mixed lymphocyte reactions, and potent graft-versus-host reactions. In addition, we found evidence for an immune response gene which controls the antibody response to bovine serum albumin. Patterns of alloreactivity observed for skin graft rejection, graft-versus-host reactivity, and mixed lymphocyte reactivity are compatible with the hypothesis that hamsters possess a major histocompatibility complex, but the absence of discernable disparity at a serologically defined locus makes a definitive statement premature.

Analysis of the major histocompatibility complex in Syrian hamsters. II. Linkage studies.

The genetic control of the histocompatibility antigens that induce strong alloreactions in Syrian hamsters was examined. Genetic studies revealed that the alloantigens involved in skin graft rejection, graft-versus-host reactions, and mixed lymphocyte reactions are under dominant single gene control and that these genetic loci are closely linked. These data suggest that this strong histocompatibility locus (i) may represent the major histocompatibility complex equivalent in this species, and this locus or group of loci has been called Hm-1. In addition, studies concerning the genetic control of the immune response to bovine serum albumin suggest that the high response is under dominant, single gene control; however, this gene is not linked to Hm-1.

Immunogenetic relationships among genetically defined, inbred domestic Syrian hamster strains.

A large number of genetically defined, isogenic strains of domestic Syrian hamsters (BIO) have been studied for their immunogenetic relationship to the inbred hamster strains MHA and CB, and to a partially inbred, recently wild strain, MIT. The results indicate that all BIO strains are histoincompatible with the inbred and recently wild strains maintained in our colony. They reject exchanged skin allografts, their lymphocytes participate in vigorous mutual mixed lymphocyte reactions. Moreover, transplantation alloantigens have been identified by serological testing with antisera recently developed by immunizing inbred hamsters with tissue from recently wild animals and vice versa. However, the incompatibility is strongest with the CB and MIT strains. Individual hamsters from many of the BIO strains accept MHA skin grafts indefinitely, fail to respond to MHA cells in mixed lymphocyte reactions, and type serologically as identical to MHA. We concluded that there must have been very little alloantigenic variation present among the three littermate hamsters caught in 1930 from which the local inbred and BIO lines are derived. Moreover, after 40 years there has been little, if any, mutational change in this restricted gene pool, at least as it can be expressed in histocompatibility assays. These findings address the issue of the extent of alloantigenic diversity among Syrian hamsters.

Induction of transplantation tolerance in rats by spleen allografts. I. Evidence that rats tolerant of spleen allografts contain two phenotypically distinct T suppressor cells.

We have examined suppressor cell activity in transplantation tolerant (TT) rats bearing vascularized spleen allografts in several different donor-recipient combinations. More than 60% of WAG (RT-1u) and 65% of AGUS (RT-1l) spleen allografts were permanently accepted when transplanted to AGUS and PVG (RT-1c) rats, respectively. All (WAG X AGUS)F1 to AGUS and (AGUS X PVG)F1 to PVG spleen allografts survived indefinitely. Unseparated LNC, TDL, and whole T cell or W3/25+, OX8- T cell populations obtained from AGUS rats bearing (WAG X AGUS)F1 spleens exhibited reduced mixed lymphocyte reaction (MLR) responses to the spleen donor, and to some extent to BN(RT1n) third-party stimulators, but responded normally to PVG.A(RT1a) stimulators. Coculture experiments demonstrated that lymph node cells (LNC) and thoracic duct lymphocytes (TDL) of TT rats contain RT1 specific suppressor cells. Furthermore, T cells isolated from all donor-recipient combinations contained two phenotypically distinct suppressor cell populations: a radiosensitive W3/25+, OX8- (Th/i) and a relatively radioresistant W3/25-, OX8+ (Ts/c). These Ts may be responsible for the maintenance of TT.

The role of class I and class II MHC antigens in the rejection of vascularized heart allografts in mice.

We have examined the role of entire major histocompatibility complex (MHC) disparity, individual class II or class I alloantigens in the rejection of vascularized heart allografts. Our results demonstrate that entire MHC, as well as both class II and class I disparities, may induce acute heart graft rejection or severe and irreversible heart muscle destruction. However, in 1 of 2 combinations differing at class II and 1 of 5 differing at class I, hearts have shown a good function greater than 100 days postgrafting. Furthermore, each donor-recipient combination has demonstrated a unique pattern of heart allograft function as well as a degree of heart muscle damage. In conclusion, these data suggest that the rejection process depends upon multiple factors such as the immune-response-gene-regulated immunoresponsiveness of the recipient as well as the expression of alloantigens on heart grafts during the induction and effector phases of the immune response.

Induction of transplantation tolerance in rats by spleen allografts. III. The role of T suppressor cells in the induction of specific unresponsiveness.

Heterotopic (WAG x AGUS)F1 spleen allografts survive indefinitely when transplanted to normal AGUS recipients and induce long-term donor-specific unresponsiveness. In this report, we have examined the immune reactivity of spleen graft recipients soon after transplantation, in an attempt to define the immunological mechanisms responsible for the induction of donor-specific unresponsiveness. Unresponsiveness develops as early as one week after splenic transplantation. T cells obtained from the recipient lymph node and spleen exhibit reduced mixed lymphocyte reaction responses to donor (WAG) but respond normally to third-party (PVG) stimulators. In contrast, T cells obtained from the spleen graft are unresponsive to both donor and third-party stimulators. Donor specific T suppressor cells (Ts) appear in the recipient's lymph node and spleen by one week posttransplantation--however, at this time antigen nonspecific suppressor cells predominate in the spleen graft. Only minimal cytotoxic T cell activity could be detected in the spleen graft, with the host spleen and lymph nodes being devoid of cytotoxic T lymphocytes. Sera obtained one or two weeks following splenic transplantation did not contain cytotoxic alloantibodies, and only a very weak response could be detected at one month. These data demonstrate that the unresponsiveness associated with the spontaneous acceptance of spleen allografts is correlated with the early induction of antigen specific Ts in recipient lymphoid tissue and the presence of nonspecific suppressor cells at the graft site.

Induction of transplantation tolerance in rats by spleen allografts. II. Evidence that W3/25+ T suppressor/inducer and OX8+ T suppressor/effector cells are required to mediate specific unresponsiveness.

The results presented in this report demonstrate that T cells, isolated from AGUS rats bearing long-term (WAG X AGUS)F1 spleen allografts adoptively transferred to irradiated AGUS recipients could not mediate the rejection of WAG hearts but rejected PVG. A hearts in acute fashion. Further, unresponsive T cells were able to suppress the capacity of adoptively transferred (40 X 10(6) normal T cells to reject WAG but not PVG.A heart allografts. We also studied the role of W3/25+ and OX8+ T cells subsets in the maintenance of unresponsiveness. Isolated W3/25+ or OX8+ unresponsive T cells were not able to mediate acute rejection, but were less effective in prolonging WAG allograft survival than the unresponsive whole T cell population, suggesting that both W3/25+ Ts1 and OX8+ Ts2 subsets were required for effective suppression in vivo. When, however, unresponsive W3/25+ T cells were infused simultaneously with normal OX8+ T cells, they could produce indefinite survival of WAG heart allografts. These results indicate that the unresponsive state induced by (WAG X AGUS)F1 spleen allografts transplanted to AGUS rats is maintained by the interaction of W3/25+ T suppressor/inducer and OX8+ T suppressor/effector cells.

Biochemical characterization of Syrian hamster cell surface alloantigens. III. Hamster alloantisera immunoprecipitate class II-like, but not class I-like, molecules.

Twelve hamster alloantisera, recently produced by mutual immunizations of domestic inbred strains and recently wild, partially inbred lines, identify two cell surface molecules, 29 and 39 kilodaltons, expressed by hamster lymphohematopoietic cells. Their expression on lymph node and spleen cells suggests that hamster T cells display cell surface class II homologues. None of the alloantisera identify putative hamster homologues of class I MHC molecules. The data are consistent with the hypothesis that hamsters possess a chromosomal region, tentatively designated Hm-1, that comprises genetic loci encoding alloantigens detectable by mixed lymphocyte reactivity and by serology, a region that resembles the I region of murine H-2.

Concentrations of linoleic acid in adipose tissue differ with age in women but not men.

Samples of adipose tissue, taken post-mortem from the anterior abdominal wall near the umbilicus, were obtained from road-accident victims in the Aberdeen area; subjects were of either sex with a wide age distribution (7-88 years). Similar samples were obtained from elderly females (mean age 77) who had died in Aberdeen Royal Infirmary from a variety of causes. Fatty acid compositions of samples were determined by capillary gas chromatography of methyl esters, which were obtained by direct esterification of the adipose tissue. The mean linoleic acid content for all samples was low compared with published values for similar samples from Europe and North America. Cumulative frequency distribution curves for linoleic acid did not differ with age in males but significant differences (P less than 0.001) occurred in females, with decreased concentrations in those aged over 60 compared to younger groups. Concentrations of trans-unsaturated fatty acids ranged between 2 and 7 per cent but did not differ significantly between groups. Low adipose concentrations of linoleic acid are regarded as a reflection of its reduced long-term dietary intake and as a risk factor for the development of coronary heart disease.

Characterization of branched-chain fatty acids from fallow deer perinephric triacylglycerols by gas chromatography-mass spectrometry.

Branched-chain fatty acids of perinephric triacylglycerols of semi-feral fallow deer (Dama dama dama) were analyzed by high resolution gas chromatography-mass spectrometry. Of the total fatty acids, 15.50% were Branched-chain components including 8.96% iso acids, mostly 14-methylpentacanoic acid, 2.85% anteiso acids and 1.73% of other monomethyl-substituted acids; dimethyl-branched acids with an iso structure (1.05%) and with an anteiso structure (0.18%) were also present. Whereas the predominant iso acids and methyl-substituted iso acids had chain lengths of 13 and 15 carbon atoms, the anteiso acids and methyl-substituted anteiso acids had chain lengths of 14 and 16 carbon atoms. Methyl substitution occurred on the even numbered carbon atoms relative to the carboxyl group. The general composition is also given of the fatty acids comprising the triacylglycerols of subcutaneous (rump area) and perinephric adipose tissue.

Identification of methyl-branched fatty acids from the triacylglycerols of subcutaneous adipose tissue of lambs.

A concentrate of branched chain fatty acids (as methyl esters) was prepared from the triacylglycerols of subcutaneous adipose tissue lipids of lambs receiving a carbohydrate-rich (cereal diet). This was accomplished by procedures which allowed the removal of unsaturated components by peroxidation and straight chain saturated components by urea-adduct formation. The concentrate was analyzed by high resolution gas chromatography in combination with mass spectrometry and was shown to consist of a complex mixture of saturated methyl-substituted fatty acids. Methyl substitution occurred on even-numbered carbon atoms (relative to the carboxyl group) and the chain lengths of the acids ranged from 10 to 18 carbon atoms. Acids with one methyl substituent in the fatty acyl chain were most abundant; di-, tri- and tetramethyl-substituted acids were also present. The biosynthesis of these methyl-substituted acids is discussed briefly.

Immunochemical characterization of Syrian hamster major histocompatibility complex homologues.

Based primarily on studies in mice and man, the organization and gene-product structures of the mammalian major histocompatibility complex (MHC) are thought to be extensively conserved. However, attempts to generalize from the specific observations of other species to Syrian hamsters have not been completely successful. Previous studies in hamsters have suggested abnormal structure, expression, and/or function of the putative hamster MHC and its products. Characterization of hamster MHC gene-products is therefore of interest. This study concerns the identification and characterization of hamster cell-surface glycoproteins homologous to MHC products of man and mouse. Utilizing radioimmunoprecipitation and serologic techniques, these molecules have been characterized with regard to molecular weight, tissue distribution and immunochemical homology to human and murine class I and II MHC products. In addition, alloantisera raised between histoincompatible hamster strains have been similarly used to identify cell-surface alloantigens of this species. The alloantisera detect cell-surface hamster molecules with immunochemical properties and tissue distribution resembling MHC class II rather than class I products. Thus, in contrast to other species, hamsters appear not to express extensively polymorphic major transplantation antigens of the class I type. Some hamster alloantigens are apparently homologous of Ia determinants since their genes are linked to Hm-1. However, other alloantigens with similar molecular weights are seemingly encoded by genes unlinked to the hamster MHC. These data support the hypothesis that the hamster MHC contains genes which encode for molecular products similar to those described in man and mouse, but that the organization and/or expression of these genes may be atypical.