Systemic natural killer activity following cardiac engraftment in the rat: lack of correlation with graft survival

The systemic NK activity was studied both in untreated rats which acutely reject allogeneic heterotopic heart grafts and in cyclosporine-treated rats which tolerate their transplants. The trend and magnitude of changes in NK activity were similar at all time points for the two animal groups. Compared to naive rats, peak NK activity was noted 7-8 days after engraftment in untreated rats and 7-12 days after engraftment in cyclosporine-treated hosts. In both groups, NK activity returned to normal levels by 3 weeks. No evidence could be found for inactivation of NK cells or their precursors in vivo in ungrafted rats undergoing cyclosporine treatment alone. These data are consistent with prior studies and suggest that non-specific cytotoxic activity does not represent a crucial force contributing to acute rejection of vascularized organ grafts.     

Suppressive effects of cyclosporin A on the induction of alloreactivity in vitro and in vivo

The purpose of the present study was the investigation of the effect of cyclosporin A (CsA) on the induction of alloreactivity in vitro and in vivo. Addition of CsA to mouse mixed lymphocyte cultures (MLC) not only inhibited lymphocyte proliferation but also prevented the generation of alloreactive cytolytic lymphocytes (CL). It was necessary to add CsA within the first 3 days of a 5-day MLC in order to achieve a significant suppressive effect. Lymphocytes, after being cultured in MLC with CsA for 4 days or longer, were incapable of being activated upon re-exposure to the same alloantigens although their responses to unrelated antigens remained intact, indicating antigen specificity of the suppression induced by CsA and its long-lasting effect. Furthermore, lymphocytes from mice treated with CsA after allosensitization failed to manifest primary cytotoxicity and could not be reactivated in a secondary MLC. Finally, CsA had no effect on those CL already generated, suggesting that CsA acts upon the induction of CL rather than the effector phase.     

Cellular components of allograft rejection: identity, specificity, and cytotoxic function of cells infiltrating acutely rejecting allografts.

Functioning mononuclear cells have been harvested from heterotopic rat cardiac allografts during maximal transplant cellular infiltration. T cells, identified by a T cell-specific absorbed rabbit anti-rat brain serum, constituted two-thirds of the total cells recovered. Approximately 20% of the infiltrating cells bear and synthesize surface immunoglobulin. Macrophages, identified by latex ingestion and morphologic and cytochemical techniques, comprise 9% of the graft infiltrate. Donor-specific cytotoxic T lymphocytes are concentrated within the graft. A separate population of Fc receptor-positive recovered cells mediate antibody-dependent LMC (Ab-LMC). Neither effector cell was adherent or phagocytic. These studies have conclusively established that cytotoxic T lymphocytes accumulate within rejecting allografts; however, the enriched presence of cytotoxic T cells within the grafts is not fully dependent upon antigen recognition per se, since Lew animals grafted with both BN and BUF hearts have Lew anti-BN and Lew anti-BUF killer cells in each graft.     

The food and feeding habits of two co-occurring marine catfish Galeichthys feliceps and G. ater (Osteichthyes: Ariidae) along the south-east coast of South Africa

The feeding-associated morphological structures of the two Galeichthys species were found to be similar in all respects. Interspecific competition for food was avoided through habitat separation. Habitat preference, as established by dietary analysis and fishing trials, was based on substratum type. Galeichthys feliceps fed over sandy and muddy substrata in marine and estuarine environments, while G. ater fed exclusively over marine reefs. The two species have different caudal fin structures which are probably evolutionary responses to habitat-associated behavioural requirements in the two different environments.
The diets of the two species were investigated and compared using calorific values of prey items. While both species fed predominantly on benthic crustaceans, polychaetes and molluscs, little dietary overlap occurred at the species level. In the estuarine environment, G. feliceps fed mainly on the anomurans Upogebia africana and Calianassa kraussi , crabs Hymenosoma orbiculare and Cleislosoma edwardsii , and several isopod species. In the marine environment G. feliceps fed mainly on two species of crabs, Thaumastoplax spiralis and Goneplax angulata , the echiurid Ochaetostoma capense and the sedentary polychaete Sternaspsis scutata. A high incidence of teleost scales in the diet of G. feliceps juveniles was found to be a consequence of scavenging rather than a lepidophagous habit. Galeichthys ater fed widely on several reef-associated crabs, isopods, polychaetes and cephalopods.