Minor Histocompatibility Loci Research Articles

High-resolution mapping of a minor histocompatibility antigen gene on mouse chromosome 2.

Minor histocompatibility (H) loci are significant tissue transplantation barriers but are poorly understood at the genetic and molecular level. We describe the construction of a high-resolution genetic map that positions a class II MHC-restricted minor H antigen locus and orders 12 other genes and genetic markers within the we-un interval of mouse Chromosome (Chr) 2. An intersubspecific backcross between B10.UW/Sn-H-3b and CAST/Ei, an inbred stock of Mus musculus castaneus, was used for this purpose. A total of 1168 backcross mice were generated, and 71 we-un recombinants were identified. Significant compression of the genetic map in males versus females and transmission distortion of CAST-derived we, un, and Aw genes were observed. Monoclonal T cell lines specific for two minor H alloantigens, Hd-1a and Hd-2a, encoded by gene(s) that map to the we-un interval were used to antigen type the backcross mice. The results suggest the Hd-1a and Hd-2a antigens are most likely encoded by a single gene, now referred to as H-3b. The determined gene order is we-0.09 +/- 0.09-Itp-0.62 +/- 0.23-D2Mit77-0.26 +/- 0.15-[Evi-4, Pcna, Prn-p]-0.26 +/- 0.15-Scg-1-0.44 +/- 0.19-[Bmp2a, D2Mit70]-0.09 +/-. 0.09-[D2Mit19, D2Mit46]-1.59 +/- 0.36-D2Mit28-0.97 +/- 0.28-D2Ler1-1.50 +/- 0.35-H-3b-0.26 +/- 0.15-un (% recombination +/- 1 SE). Because the average resolution of the backcross is 0.09 cM, the backcross panel should facilitate the physical mapping and molecular identification of a number of genes in this chromosome region.

Certain Host-Donor Rat Strain Combinations Do Not Reject Brain Allografts after Systemic Sensitization

To investigate the factors related to allogenic brain graft rejection, rat cortex from either LEW-RT1l or BN-RT1n rats was transplanted into brains of several isogenic and allogenic inbred strains: F344-RT1l, LEW-RT1l, BN-RT1n, AO-RT1u, PVG-RT1c, PVG-RT1u, and PVG-RT1l. Each donor and host combination was subsequently subdivided into two subgroups. One group was systematically sensitized twice with donor skin tissue and another group served as a sham-sensitization control. Four weeks after the second sensitization, host brains were examined histologically, and the percentage volume of each graft that showed increased cellularity was estimated. Expression of major histocompatibility complex (MHC) and T cell antigens was also studied immunocytochemically. Almost all grafts in sham-sensitized animals from all groups were accepted with minimal or no reaction. However, two strains (AO-RT1u and F344-RT1l) showed considerable cell infiltration and expression of MHC antigens even without sensitization. After sensitization, almost all allogenic strain combinations showed greater signs of rejection-related responses. The severity of the tissue reaction, however, varied considerably between groups. All grafts from BN-RT1n donors were rejected severely in all host strains. For LEW-RT1l donors, grafts survived well in some host strains (BN-RT1n, AO-RT1u, PVG-RT1c, and PVG-RT1u), even with MHC + nonMHC disparity. Curiously, F344-RT1l hosts rejected LEW-RT1l grafts even though the two strains have the same MHC loci, but different minor histocompatibility (mH) loci. For both donor strains, experimental autoimmune encephalomyelitis-susceptible hosts tended to show more vigorous rejection responses. Histological data indicated that CD4+ cells were the predominant infiltrating cell type(s). These cells appeared to be primarily blood-derived macrophages and microglia. Relatively few CD8+ cells were present even in grafts with severe immune reactions. Our results suggest that MHC disparity is not the only factor affecting the survival of allogenic neural grafts, with or without systemic sensitization, and in fact plays a relatively limited role. It is suggested that susceptibility to neural graft rejection depends on a number of factors, most importantly haplotype of the donor, but also including Ir gene, host MHC allele, and host susceptibility to autoimmune disease.

Immunological Resorption in Botryllus schlosseri (Tunicata) Chimeras is Characterized by Multilevel Hierarchial Organization of Histocompatibility Alleles. A Speculative Endeavor.

Laboratory studies on chimeras ofthe tunicate Botryllus schlosseri revealed the phenomenon of "allogeneic resorption" or "colony resorption," the elimination of one partner in a chimera. A hypothesis outlining the genetic basis of the resorption phenomenon is presented here. It proposes that allogeneic resorption in Botryllus is controlled by a polymorphic, ladder-like, tri-level hierarchial system of histocompatibility loci, with codominantly expressed alleles. The relative state of homozygosity at these alleles within each level reflects the state of the hierarchy in the resorption phenomenon. The Fu/HC haplotype of the tunicates serves as the first level, whereas the other two levels are each controlled by specific resorption alleles (Re/HC) that operate only after a response has failed to occur at previous levels. Some morphologically expressed similarities to murine minor histocompatibility loci (Hh-1 and Mls) are discussed.

A monoclonal antibody to the interleukin-2 receptor enhances the survival of neural allografts: A time-course study

A time-course study of the survival and immunological characteristics of rat neural allografts was undertaken in animals treated with a murine monoclonal antibody to the α-chain (p55) of the rat interleukin-2 receptor. This antibody, NDS 63, was administered for ten days following grafting beginning on the day of operation. Inbred rat strains differing at both major and minor histocompatibility loci were selected as donor and host. Furthermore, the recipient strain displayed a high responder major histocompatibility complex haplotype. All grafts were placed in the lateral ventricle. Comparison was drawn between NDS 63-treated recipients and two groups of controls; an untreated group and a second group treated with the monoclonal antibody NDS 66, directed at a second epitope on the α-chain of the interleukin-2 receptor, which has been shown to be ineffective in competing with interleukin-2 for binding. Immunocytochemical analysis of the transplants was performed at several time-points up to 150 days following grafting. Grafts of NDS 63-treated recipients exhibited 100% survival with minimal induction of major histocompatibility complex antigens (both class I and class II) and negligible leukocyte infiltration at all time-points studied. In contrast grafts from both groups of controls showed evidence of a chronic immune response with most grafts undergoing rejection as shown by markedly elevated major histocompatibility complex antigen expression accompanied by specific immune cell infiltration. This was a protracted process with several grafts undergoing complete rejection by 60 days and a majority, but not all, by 150 days after transplantation. It is concluded that NDS 63, a monoclonal antibody to the interleukin-2 receptor, may diminish the immune response to transplanted allogeneic neural tissue and thereby enhance its prospects for long-term survival.

Further evaluation of the pregnancy-linked down-regulation of the paternal antigen-specific splenic cytotoxic T lymphocyte activity in allogeneically pregnant mice.

Cytotoxic T lymphocyte (CTL) activity directed against paternal alloantigen was examined in allogeneically pregnant mice using various allogeneic combinations. The spleen cells from pregnant C57BL/6 (H-2b) mice mated with BALB/c (H-2d) male mice generated less anti-H-2d CTL after in vitro sensitization than those from unpregnant or syngeneically mated C57BL/6 mice. Different allogeneic combinations including the incompatibility at only D region of H-2 or minor histocompatibility loci were effective for downregulating the anti-paternal CTL activity in pregnancy. The downregulation of anti-paternal CTL activity induced by allogeneic pregnancy occurred at day 10 to day 18 of pregnancy, most extensively at day 14. The allogeneic pregnancy also downregulated the allogeneic CTL activities that had been amplified by injecting alloantigens before mating.

What are minor histocompatibility loci? A new look at an old question

In this article, Derry Roopenian relates the traditional view of minor histocompatibility ( H) loci to recent advances in understanding of the tissue rejection process and the molecular nature of minor histocompatibility antigens. He proposes that minor H loci can be subdivided by the ability of their products to stimulate different T-cell subsets and discusses the implications of this concept in terms of the origins and behavior of minor H loci and their antigens, tumor immunology and autoimmunity.

Minor histocompatibility antigens

Histocompatibility antigens have been studied for over 50 years because they form a major obstacle to clinical transplantation. Human minor histocompatibility antigens remain ill-defined, but minor histocompatibility loci have been mapped on nearly every mouse chromosome. Recent molecular definition of several transplantation antigens suggests that they are by-products of an immune system poised to present viral antigens, and a mutation in any gene may give rise to a new minor histocompatibility antigen.

Ia Restriction Specificity of KLH‐Specific T Cells from Allogeneic Bone Marrow Chimeras Is Influenced by Histocompatibility at the H‐2 and Minor Histocompatibility Loci

Ia restriction specificity involved in T cell proliferative responses to keyhole limpet hemocyanin (KLH) has been analyzed using a variety of allogeneic bone marrow chimeras. The chimeric mice were prepared by reconstituting irradiated AKR, SJL, B10.BR and B10.A(4R) mice with bone marrow cells from B10 mice. When such chimeric mice had first been primed with KLH in complete Freund's adjuvant (CFA), T cells from H-2 incompatible fully allogeneic chimeras showed significantly higher responses to KLH in the presence of antigen-presenting cells (APC) of donor strain (B10) than APC of recipient strain. However, in H-2 subregion compatible chimeras, [B10----B10.A(4R)], which were matched at the H-2D locus and at minor histocompatible loci, the T cells could mount vigorous responses to KLH with antigen-presenting cells (APC) of either donor or recipient type. The same results were obtained as well with chimeras that had been thymectomized after full reconstitution of lymphoid tissues by donor-derived cells. A considerable proportion of KLH-specific T cell hybridomas established from [B10----B10.A(4R)] chimeras exhibited both I-Ab and I-Ak restriction specificities. The present findings indicate that the bias to donor Ia type of antigen specific T cells is determined by donor-derived APC present in the extrathymic environment but that cross-reactivity to the recipient Ia is influenced to some degree by histocompatibility between donor and recipient mice, even though the histocompatible H-2D locus and minor histocompatibility loci seem not to be directly involved in the I-A restricted responses studied herein.

The Treatment of Peripheral Nerve Injuries Using Irradiated Allografts and Temporary Host Immunosuppression (in a Rat Model)

Irradiation of allografts prior to transplantation and host immunosuppression with cyclosporin-A were studied separately and in combination as means of lessening the rejection of transplanted peripheral nerve tissue. Lewis and Brown Norway rats were used in the animal model, as they differ at both major and minor histocompatibility loci. Sciatic nerve grafts (2.5 cm) were used and the animals were followed for 16 weeks after nerve grafting. The outcome was studied by functional measurements (sensory testing, gait analysis, joint flexion contracture, and muscle weight), as well as by measurements of biochemical and histologic parameters (hydroxyproline concentration and axon counts, respectively). Sensory testing was not reliable because of crossover innervation by the saphenous nerve. Evaluation by standard gait-testing techniques was found to be unsatisfactory. However, the allografted animals receiving cyclosporin-A had significantly smaller flexion contractures, compared to the allografted animals without immunosuppression (17 degrees +/- 12 degrees vs. 44 degrees +/- 13 degrees and 51 degrees +/- 13 degrees, p less than 0.005). Allografted animals receiving short-term cyclosporin-A had contractures that were not significantly different from those seen in isografted control animals (17 degrees +/- 12 degrees vs. 22 degrees +/- 15 degrees, NS). Muscle hydroxyproline concentration analysis revealed a lower hydroxyproline concentration among the allografted groups that received irradiated allografts, compared to groups receiving nonirradiated allogeneic grafts. The studies of muscle hydroxyproline concentration and muscle weight both showed substantial reinnervation, even in allografted animals without pretreatment of the grafts or immunosuppression of the recipient animal.(ABSTRACT TRUNCATED AT 250 WORDS)

ALTERATIONS IN T CELL-DERIVED COLONY-STIMULATING FACTORS ASSOCIATED WITH GVH-INDUCED IMMUNE DEFICIENCY

Injection of parental C57BL/10 spleen cells into unirradiated immune-competent (B10 x B10.BR)F1 hosts has been demonstrated to produce a graft-vs.-host-induced immune deficiency in T cell-mediated functions, including mitogen or alloantigen stimulated proliferation or cytotoxic T cell generation. The production of T cell-derived lymphokines affecting hematopoiesis was also altered during GVH. During the first two weeks of GVH, IL-3 and particularly GM-CSF were produced spontaneously; in subsequent weeks, the spontaneous production dropped to normal or subnormal levels. CSF content in concanavalin A-stimulated splenic supernatants was reduced at weeks 1-2, and declined to less than 5% of normal levels by 3-4 weeks of GVH. This decline in CSF content was correlated with a decrease in immune function as assessed by concanavalin A-stimulated IL-2 production and by generation of cytotoxic T lymphocytes. Concurrent with the recovery of immune function during GVH weeks 8-15, mitogen-stimulated production of CSF returned to normal levels. In addition to the decrease in CSF production identified in acute suppressive GVH, CSF content in concanavalin A-stimulated splenic supernatants was also decreased in chronic stimulatory GVH, generated in the strain combination (B6 x B6bm1)F1----(B6bm1 x B6bm12)F1. This decrease in CSF production correlated with a decrease in self-restricted T helper cell function. Finally, a decrease in both immune function and CSF production capacity was observed in the acute GVH following allogeneic (minor histocompatibility loci) bone marrow transplantation into irradiated hosts.

Complexity at the mouse minor histocompatibility locusH-4

The fine immunogenetics of the chromosome 7 mouse minor histocompatibility (H) locus H-4 was investigated. Both class I major histocompatibility complex (MHC)-restricted cytotoxic T lymphocytes (CTL) and class II MHC-restricted "helper" T cells (TH) specifically reactive with H-4 antigens were isolated as clones and were used as genetic probes for classical backcross segregation analysis. Results of a four point cross indicated that the H-4 locus was actually comprised of two genes, that have been designated H-46 and H-47. The former encodes antigens recognized by the TH and the latter encodes antigens recognized by the CTL. Moreover, these two genes could be separated from the gene pink-eyed dilution (p) which was found to be "sandwiched" between them. The functional significance of a minor H congenic strain differing by both TH-defined H-46 and CTL-defined H-47 was addressed using F1 complementation tests. Such studies indicated that immune responses against H-46 antigens was required for generation of H-47-specific CTL. Altogether, these results suggest selective presentation of different minor H gene products by class I or class II MHC proteins and that the minor H "locus" H-4 may have necessarily included both TH and CTL-defined genes because of requisite TH-CTL collaboration.

Responses against antigens encoded by theH-3 histocompatibility locus: Antigens stimulating class I MHC- and class II MHC-restricted T cells are encoded by separate genes

The purpose of this work was to study the genetic basis of histocompatibility antigens encoded by the mouse minor histocompatibility (H) locus H-3. Both class I major histocompatibility complex (MHC)-restricted cytotoxic T lymphocytes (CTL) and class II MHC-restricted helper T cells (TH) specific for antigens encoded by genes within the H-3 locus were isolated and analyzed. Typing a number of mouse strains for expression of antigens recognized by these TH and CTL suggested that there was a different strain distribution pattern of expression of the antigens recognized by TH compared with those recognized by CTL. Separation of the genes whose products stimulate TH from those whose products stimulate CTL was suggested by: (1) analysis of the strain B10.FS(92NX)/Grf that has undergone recombination within the H-3 region; (2) genetic segregation studies of (B10.UW-H-3b/Sn x C57BL/10Sn)F2 mice; and (3) F1 complementation studies in which CTL specific for products of the TH-defined gene(s) could not be detected, even in the absence of immune responses to products of the CTL-defined genes. Taken together, these data suggest that in addition to two genes (B2m and Cd-1) within the H-3 region whose products typically stimulate class I MHC-restricted CTL, there is at least one additional gene whose product selectively stimulates class II MHC-restricted TH. This new gene is located telomeric from the CTL-defined genes and between the loci we and un on chromosome 2. These data demonstrate a novel degree of complexity of the H-3 "locus" and suggest selective presentation of minor H gene products in the context of class I or class II MHC proteins.

The Indirect Effects of Cytomegalovirus Infection on the Outcome of Organ Transplantation

The evolution of organ transplantation from an interesting experiment in human immunobiology to a highly successful, practical approach for rehabilitating patients with end-stage kidney, heart, liver, and lung disease is one of the great successes of modern medicine. However, the very success of organ transplantation has created in an ever-increasing number of individuals a series of phenomena that have no precedent in medicine or biology: (1) the long-term presence of vascularized organs that differ from the host at a variety of major and minor histocompatibility loci, (2) the lifelong intake of broadly active immunosuppressive agents to permit the continued function of the allograft, and (3) the reactivation, tissue invasion, and continued proliferation of certain infectious agents, particularly the herpes group of viruses, within the individual. The net result of these phenomena are a series of clinical syndromes and effects that are unique to the transplant recipient. Among the most important

Fetal pancreas transplantation in miniature swine. II. Survival of fetal pig pancreas allografts cultured at room temperature.

Islet-allograft survival has been shown to be markedly prolonged in rodents when donor tissue has been precultured at 24 degrees C. In this study, the feasibility of this approach was tested in NIH minipigs transplanted with fetal pancreases. Collagenase-digested fetal pig pancreatic tissues survived in culture at 24 degrees C for 6-7 days and continued to grow in vitro at 37 degrees C after being transferred. These tissues no longer stimulated allogeneic lymphocytes in vitro, although some tissues cultured at 37 degrees C did. This allogeneic stimulation did not correlate to the number of major histocompatibility complex (MHC) class II-positive cells in stimulator pancreatic cultures. When transplanted into an omentum pouch of normal, nonimmunosuppressed minipigs, fresh fetal pancreatic tissues were rejected within 14 days. Tissues cultured at 24 degrees C grew, and beta-cells proliferated in minipigs treated daily with cyclosporin A (CsA) and azathioprine. Twelve normal minipigs were transplanted with 24 degrees C-cultured fetal pancreases: 8 pigs received no treatment, 2 received 14 mg.kg-1.day-1 CsA for 14 days, and 2 received 6-7 intravenous injections of platelets prepared from pooled farm-pig blood before grafting. Strong lymphocytic infiltration was detected in all grafts removed between 30 and 90 days posttransplantation. However, beta-cells were found on day 45 in one of five minipig pancreas grafts incompatible at the MHC loci and on days 60-90 in all three grafts compatible at MHC but incompatible at minor histocompatibility loci. Short-term CsA treatment did not prolong survival of allografts from farm pigs into minipigs.(ABSTRACT TRUNCATED AT 250 WORDS)

Generation of helper cell-independent cytotoxic T lymphocytes is dependent upon L3T4+ helper T cells.

The role of L3T4+ (CD4+) Th cells in generation of CTL specific for discrete minor histocompatibility Ag was investigated. Suppression of the function of Th cells in vivo by chronic treatment with anti-L3T4 mAb prevented congenic strains of mice from being primed and from generating CTL specific for Ag encoded by the minor histocompatibility loci--H-3, H-1, and B2m. Analysis of proliferative responses and lymphokine secretion of cells from animals primed with one of these minor H Ag, beta 2-microglobulin, but not treated with anti-L3T4 antibodies, indicated that L3T4- class I MHC-restricted T cells were themselves responsible for the very great majority of the observed minor H Ag-specific proliferation and secretion of lymphokines associated with both T cell proliferation and activation of CTL. All together, the data indicate that in responses against discrete minor H Ag, L3T4+Th-independent CTL are generated through an L3T4+Th-dependent pathway.

Effects of thyroxine-driven precocious metamorphosis on maturation of adult-type allograft rejection responses in early thyroidectomized frogs

Abstract In contrast to the adult pattern of allograft reactivity, larval South African clawed frogs ( Xenopus) either become tolerant of adult major histocompatibility complex (MHC) disparate skin grafts or reject them slowly. Larvae fail to reject grafts that are incompatible at minor histocompatibility (H) loci (MHC-identical); rather, they become immunologically tolerant. We report here that early thyroidectomized (thyroidx) larvae, forced to metamorphose precociously on a regimen of thyroxine (T 4) treatment, showed larva-like responses in that their ability to reject skin allografts that differed by minor H loci or one MHC haplotype was significantly impaired relative to agematched intact postmetamorphic controls. During the normal ontogeny of Xenopus, lymphocyte numbers increase in larval life, decrease during metamorphosis, and increase to adult levels at 6-12 months of age. Thyroidectomy and a low-dose regimen of thyroxine treatment limited the number of lymphocytes that developed in larval organs and very dramatically reduced those populations below control levels during metamorphosis. Because these changes were stage-dependent rather than age-dependent, the second wave of lymphopoiesis in thyroidx frogs treated with low T 4 may occur out of synchrony with the expression of Class I MHC antigens. Impaired allograft rejection, therefore, may reflect the absence of a population of cells that can effectively recognize minor H alloantigens and/or self and allo Class I antigens.

Augmentation of donor bone marrow engraftment in histoincompatible murine recipients by granulocyte/macrophage colony-stimulating factor

T cell depletion of donor bone marrow can prevent graft v host disease (GVHD) in human and murine marrow graft recipients. However, engraftment in the recipient may be compromised as a consequence of donor marrow T cell depletion. The effect of recombinant murine granulocyte/macrophage colony-stimulating factor (rmu GM-CSF) on engraftment and hematologic reconstitution was evaluated in a murine allogeneic bone marrow transplantation (BMT) model involving T cell depletion of marrow. Before transplantation into irradiated mice differing at major and minor histocompatibility loci, rmu GM-CSF was preincubated with T cell-depleted donor marrow. When low degrees of engraftment were noted in control recipients, treatment of donor marrow with high concentrations of rmu GM-CSF led to enhanced engraftment. Ex vivo donor graft incubation with rmu GM-CSF or a single in vivo injection of rmu GM-CSF were both effective means of promoting engraftment. When the engraftment rate in control recipients was high, rmu GM-CSF did not have an identifiable effect. Only slight increases in hematologic recovery were detected regardless of the rate of engraftment. Neither post-BMT survival nor marrow stem cell capacity was affected by rmu GM-CSF incubation. Furthermore, growth factor administration did not have a significant effect on the incidence of GVHD in recipients of non-T cell-depleted bone marrow splenocyte preparations. In vitro natural killer-mediated target cell lysis was not altered by incubation of effector cells with rmu GM-CSF. These results demonstrate the potential of ex vivo rmu GM-CSF treatment of donor marrow to facilitate engraftment across extensive histo- compatibility barriers.

Augmentation of Donor Bone Marrow Engraftment in Histoincompatible Murine Recipients by Granulocyte/Macrophage Colony-Stimulating Factor

AbstractT cell depletion of donor bone marrow can prevent graft v host disease (GVHD) in human and murine marrow graft recipients. However, engraftment in the recipient may be compromised as a consequence of donor marrow T cell depletion. The effect of recombinant murine granulocyte/ macrophage colony-stimulating factor (rmu GM-CSF) on engraftment and hematologic reconstitution was evaluated in a murine allogeneic bone marrow transplantation (BMT) model involving T cell depletion of marrow. Before transplantation into irradiated mice differing at major and minor histocompatibility loci, rmu GM-CSF was preincubated with T cell-depleted donor marrow. When low degrees of engraftment were noted in control recipients, treatment of donor marrow with high concentrations of rmu GM-CSF led to enhanced engraftment. Ex vivo donor graft incubation with rmu GM-CSF or a single in vivo injection of rmu GM-CSF were both effective means of promoting engraftment. When the engraftment rate in control recipients was high, rmu GM-CSF did not have an identifiable effect. Only slight increases in hematologic recovery were detected regardless of the rate of engraftment. Neither post-BMT survival nor marrow stem cell capacity was affected by rmu GM-CSF incubation. Furthermore, growth factor administration did not have a significant effect on the incidence of GVHD in recipients of non-T cell-depleted bone marrow/ splenocyte preparations. In vitro natural killer-mediated target cell lysis was not altered by incubation of effector cells with rmu GM-CSF. These results demonstrate the potential of ex vivo rmu GM-CSF treatment of donor marrow to facilitate engraftment across extensive histocompatibility barriers.©1988 by Grune & Stratton, Inc. 0006-4971/88/7102-0002S3.00/0

Effector mechanism in rejection of allografts expressing an isolated minor histocompatibility disparity. Importance of cytotoxic T lymphocytes in the rejection of H-43a allografts by H-43b mice.

To explore effector mechanisms in allograft rejection, we transplanted skin grafts (SG) across a single minor histocompatibility locus (H-43) using mouse strains carrying the H-43b allele as SG recipients and those carrying the H-43a allele as SG donors. Recipients' spleen cells (SC) were assayed at various intervals for 200 days for anti-H-43a cytotoxic T lymphocyte (CTL) responsiveness, as well as delayed-type hypersensitivity (DTH) responsiveness. When H-43a SG from C3H.SW mice were transplanted to H-43b CWB mice, two thirds of the recipients rejected the SG, and recipients' SC showed marked self-H-2Kb-restricted anti-H-43a CTL responsiveness until the end of the observation period. In contrast,H-43aSG transplanted to H-43b (B10.BRxCWB)F1 (BWF1) mice survived in almost all of the BWF1 recipients. The anti-H-43a CTL responsiveness of the recipients' SC was evident until day 40 but thereafter started to wane and eventually disappeared. Notably, BWF1 mice whose self-H-2Kb-restricted anti-H-43a CTL precursors had been primed by prior injection with H-43a SC rejected H-2Kb-bearing H-43a CSW SG but not H-2k, H-43a C3H/HeN SG. In contrast, an anti-H-43a DTH response was not induced in any of the CWB and BWF1 recipients, including CWB recipients who rejected the H-43a SG. Since it has been well documented that anti-H-43a CTL are restricted solely by self-H-2Kb, the results in this study indicate that self-H-2Kb-restricted anti-H-43a CTL are responsible for rejection of H-43a allografts by H-43b recipient mice.

BONE MARROW TRANSPLANTATION WITH T-CELL-DEPLETED GRAFTS

Graft-versus-host disease (GVHD), a serious complication of allogeneic bone marrow transplantation (BMT), can be prevented by in vitro depletion of T cells from the bone marrow (BM) prior to transplantation. The purpose of this study was to assess the role of BMT cells in the reconstitution of various immune functions following BMT across minor histocompatibility barriers. Lethally irradiated CBA/J (H-2k) mice were grafted with either 10(7) unseparated or T-cell-depleted BM cells from B10.BR (H-2k, minor-histoincompatible) mice. Blood counts, BM colonies in agar, and various immune functions of spleen cells from the recipient mice were tested 2-12 weeks post-BMT and compared with those of normal donors. The following observations were made: (A) Peripheral blood lymphocyte counts decreased to 30% of normal 2 weeks post-BMT with almost normal recovery at 8 weeks. (B) The percentage of Thy1.2+ splenocytes reached normal levels at 8 weeks post-BMT. (C) The number of BM colonies (GM-CFU) was reduced to 10% at 2 weeks and fully recovered at 12 weeks. (D) Proliferative response to the B-cell mitogen LPS was fully reconstituted after 4 weeks; however, anti-SRBC PFC (following Mishell-Dutton cultures) was restored 50% at 8-12 weeks. (E) Reconstitution of T cell functions including proliferative responses to concanavalin A, phytohemagglutinin, and allogeneic leukocytes, and allocytotoxicity, did not exceed 50% even 12 weeks post-BMT. Overall, depletion of T cells from donor BM allografts incompatible at minor histocompatibility loci, did not seem to significantly alter the rate of immunohematopoietic reconstitution in the lethally irradiated BM recipients.