Ichiro Nakamura

Bat-1 genes and the origin of multiple class I loci in the H-2D region

The structural organization of the H-2 complex, particularly in the telomeric class I regions D, Q, and TL, is subject to considerable variation from one haplotype to another. In the H-2b and H-2k haplotypes, and presumably in most other haplotypes, the D region consists of a single class I locus (Weiss et al. 1984; Stephan et al. 1986). In the H-2d and H-2q, and presumably in H-2v, the D region contains five class I loci, D, D2, D3, D4, and L (Stephan et al. 1986; Duran et al. 1989; Rubocki et al. 1990). Thus, the H-2D region appears to have two basic types of configuration. However, as additional haplotypes are analyzed in detail, evidence for the existence of other configurations begins to emerge (Rubocki et al. 1990; Cai and Pease 1992; Tummuru et al. 1992). Recently, we located a mouse homologue of the human BAT1 locus, one of the new HLA genes found in the class Ill region of the HLA complex, in close proximity to the Db gene (Wroblewski et al. 1990). The distance between the Tnfgene cluster and the mouse Bat-1 locus is about 40 kilobases (kb), as in the HLA complex, suggesting that this interval is well preserved among species. In contrast, the interval between Bat-1 and the closest distal class I locus is about 10 kb in the H-2b, as opposed to 170 kb in the HLA complex. Thus, it seemed likely that the known difference of approximately 10 kb in the size of the Tnf cluster/D locus interval in the H-2b (Wroblewski et al. 1990) and the H-2ct (Mtiller et al. 1987) reflects a variability in the Bat-1/D interval. The five locus configuration of the H-2D d region may have been derived from an unequal crossover event, as proposed earlier (Stephan et al. 1986; Rubocki et al. 1990). According to this hypothesis, the L locus was derived from the D locus. This proposal rests on the strong sequence similarities between the flanking sequences of D a and L d on

The B144-H-2Db interval and the location of a mouse homologue of the human D6S81E locus

The major histocompatibility complex (MHC) encodes the class I/II cell surface molecules that provide the context for T-lymphocyte recognition of nominal antigens and other molecules (class III) of unrelated functions. The H-2 complex, the mouse MHC, has been the subject of extensive studies, yet a major gap remains in our understanding of its physical structure between the S and the D regions. According to a recent estimate, this interval is at least 350 kilobases (kb) long (Mfiller et al. 1987b). There are haplotype-dependent differences in the class I gene organization of the H-2D region (Weiss et al. 1984; Stephan et al. 1986). In the H-2 d haplotype, the evolutionarily related and closely linked tumor necrosis factor (Tnfa) and lymphotoxin (Tnfb) genes are located approximately 70 kb centromeric to the proximal class I locus, H-2D (Mfiller et al. 1987a). The Tnfgene pair is also present in H-2 b, although its exact location is not known (Gardner et al. 1987). B144, a gene of unknown function, is located about 10 kb proximal to the Tnfgenes in H-2 d (Tsuge et al. 1987). Thus, the proximal section of the D region between the B144 and D loci in haplotypes other than H-2 d remains incompletely defined. Recently, a series of non-class I/II genes was identified in the HLA complex within the interval corresponding to mouse H-2S/D (Spies et al. 1989a, b; Sargent et al. 1989a, b). Pending identification of the functions of these genes, they are known as HLA-B-associated transcript I through 9 (BAT1-BAT9; Spies et al. 1989a, b) and G1 through GIO (Sargent et al. 1989a), or officially by the D-series nomenclature for anonymous loci (Spence et al. 1989). For further understanding of the function and evolution of the MHC genes and of their organization, it is essential to determine if homologous genes exist in other species, particularly in the mouse.

Genetic control of the target structures recognized in hybrid resistance

Hybrid resistance of lethally irradiated (C57BL/6 × DBA/2)F1 and (C57BL/10 × C3H)F1 hybrid mice to the engraftment of parental C57BL/6 or C57BL/10 bone marrow cells is controlled by the H-2-linked Hh-1 locus. This resistance can be specifically blocked or inhibited by the injection of irradiated spleen cells from lethally irradiated, marrow reconstituted donor mice of certain strains. By testing the ability of regenerating spleen cells from various donor strains to block the resistance, we studied the genetic requirements for the expression of putative cell-surface structures recognized in hybrid resistance to H-2b marrow cells. Strains of mice bearing informative intra-H-2 or H-2/Qa-Tla recombinant haplotypes provided evidence that the Hh-1 locus is located telomeric to the H-2S region complement loci and centromeric to the H-2D region class I locus in the H-2b chromosome. Two mutations that affect the class I H-2Db gene have no effect on Hh-1b gene expression. The H-2D region of the H-2S haplotype contains an allele of the Hh-1 locus indistinguishable from that of the H-2Db region, as judged by the phenotypes of relevant strains and F1 hybrids. Collectively these data indicate that the Hh-1 locus is distinct from the class I H-2D (L) locus in the H-2b or H-2s genome, and favor the view that the expression or recognition of the relevant determinants is not associated with class I gene products.

Cellular suppression of murine ADCC and NK activities induced by Corynebacterium parvum

SummaryAdministration of a single dose of C. parvum (CP) induces depression of splenic NK activity in mice after a lag period of 3–5 days and this depression lasts about 2 weeks. The depressed levels of NK activity noted in this study depended on time of CP administration and were associated with the induction of suppressor cell activity. Neonatally thymectomized or sublethally irradiated mice had unimpaired ability to generate suppressor cells following CP treatment. Depletion of adherent/phagocytic cells by carbonyl iron plus magnetism, Sephadex G-10 filtration, or both neither enriched NK activity nor removed suppressor activity from the spleens of CP-treated mice. Antibody-dependent cellular cytotoxicity (ADCC) against lymphoma targets was also depressed in CP-treated mice, accompanied by a concomitant appearance of suppressor cells that interfere with ADCC at the effector level.

Involvement of Natural Effector Cells in Bone Marrow Transplantation and Hybrid Resistance

Natural resistance to hemopoietic allograft can be defined as the nonadaptive host reaction that causes graft failure in a nonimmunized host. Such restrictions notwithstanding, the phenomenon is heterogenous and can encompass a variety of effector mechanisms directed against distinct cell surface entities. The key word is “nonadaptive.” However, since the nonadaptive nature of a reaction cannot always be tested, misinterpretation can result. Exposure of the prospective allograft recipients to a lethal dose of ionizing radiation does not completely eliminate the adaptive components of the host immune system.(1,2) Although conventional effector mechanisms by T and B lymphocytes are excluded by the above definition, these cells may play a role as a secondary component or as regulators of nonadaptive responses. Therefore, the study of natural resistance to hemopoietic cells must take into account the possible multiplicity of the effector mechanisms and the complexity of regulatory influences. Our inability to define the mechanisms precisely and to understand the factors influencing the ultimate fate of the grafted cells has led to conflicting interpretations of the unique phenomenon discovered nearly 30 years ago by Snell, Boyse, Cudkowickz, and other pioneers.(3-8) For a comprehensive treatment of this subject, the reader is referred to the excellent review recently written by Bennett.(9)

Suppression of murine NK activity induced by Corynebacterium parvum

SummaryFormalin-killed Corynebacterium parvum (CP), given at a dose of 0.4–0.7 mg/mouse IV or IP, induced suppressor cells for NK activity in B6C3F1 mice. The suppressor cells belong to at least two different populations, plastic adherent and nonadherent, and were not depleted by antibodies specific for Thy-1.2, Iak, or NK-1.2 surface markers. Administration of p-I:C, an interferon-inducer, to animals 18 h before the assay did not affect the suppressor activity. Hypotonic shock treatment of splenocytes abrogated the in vitro suppressive activity, and subsequent reconstitution of the shock-treated cells with RBC failed to restore the suppressive activity. SJL/J mice, which have low NK activity, exhibited suppressor activity comparable to B6C3F1 mice following CP treatment, whereas CP-treated BALB/c athymic and euthymic mice showed a lower ability to generate suppressors for NK as compared to B6C3F1 mice.

F 1 ANTI-PARENT CELL-MEDIATED LYMPHOLYSIS: AUTOREACTIVE EFFECTORS AND REQUIREMENT OF PARENTAL T CELLS FOR STIMULATION

Publisher Summary This chapter discusses the importance of autoreactive effectors and the requirement of parental T cells for stimulation. Responder spleen cells of B6D2F1 hybrid mice cultured in vitro with irradiated parental B6 SC generate cytotoxic T lymphocytes that specifically lyse target cells sharing H-2 antigens with the parental stimulators. The chapter discusses three main issues related to the in vitro development of F1 anti-parent cell-mediated lympholysis (CML): (1) identification of the genetic region of the H-2 complex coding for or regulating the expression of target determinants, (2) recognition of the autoreactive nature of the response, and (3) requirement of irradiated parental T cells for induction of F1 anti-parent CTL.