Heterologous antisera to Lyt-1+, 2- -derived antigen-binding factor detect a subfactor of an antigen-specific suppressor factor and cell surface proteins on Lyt-1+, 2- and Lyt-1-, 2+ T cells

Rabbits were immunized with TNP-specific Lyt-1+, 2- T cell-derived, antigen-binding proteins (PCI-F) released by T cells sensitized by skin painting with picrylchloride. The resulting antiserum (anti-PCI-F) bound to PCI-F and TNP-specific factors that suppressed delayed hypersensitivity (TSF) known to be comprised of PCI-F and Lyt-2+ -derived polypeptides released by cells sensitized by injection of trinitrobenzenesulfonic acid (TNBSF). Anti-PCI-F bound to T lymphocytes and 68,000 to 72,000 m.w. T cell surface proteins but not B cells on their surface proteins. Anti-PCI-F bound to both Lyt-1+ and Lyt-2+ T cells and surface proteins. A comparison of anti-PCI-F with anti-TSF indicates that anti-TSF contains specificity for Ly-2+ T cell-derived components of TSF and T cells not present in anti-PCI-F. The possibility of multiple isotypes of T cell receptors and antigen-binding molecules is discussed.     

Allogeneic T-cytotoxic reactivity of senescent mice: affinity for target cells and determination of cell number

Experiments were performed to determine the cause(s) of the reduced T-cytotoxic-cell response observed in senescent mice. The cytotoxic cells studied developed in mixed lymphocyte cultures (MLC) of 6 × 10⁶ C57B1/6J (H-2^b) spleen cells from mice of various ages which were stimulated by doses of irradiated Balb/c (H-2^d) cells giving responder to stimulator ratios of 10:10 and 10:1. The cytotoxic response, as determined in a ⁵¹Cr-release assay against P815 (H-2^d) mastocytoma cells in culture, declines with age. This age-related decline is more pronounced with the lower dose of stimulator cells (10:1). The cytotoxic response developing in 10:10 and 10:1 MLC of spleen cells from young mice is comparable in magnitude, whereas the lower dose (10:1) is much less stimulatory in cultures of spleen cells from mice above 12 months of age. In order to better understand this age-dependent decline in cytotoxic response, the affinity of effector cells to their target and the percentage of cytotoxic cells which develop in the cultures of spleen cells from mice of various ages were determined. The affinity of cytotoxic cells developing in 10:10 MLC does not change with age. The affinity of cytotoxic cells developing in 10:1 MLC from young mice is significantly higher than the affinity of those developing in 10:10 MLC. This dose-dependent increase in affinity is not apparent in 20-month-old mice, which show equal affinity of cytotoxic cells in 10:10 and 10:1 MLC. The percentage of cytotoxic cells in the cultures was found to decrease with age. This decrease was more pronounced after 10:1 stimulation. Thus the decline with age in cytotoxic response can be attributed to a decrease in number of functional cytotoxic cells developing in MLC cultures, regardless of stimulator cell dose and a decrease in affinity for target cells at low stimulator cell doses.     

Developmental potential of neural crest-derived cells migrating from segments of developing quail bowel back-grafted into younger chick host embryos

The technique of back-transplantation was used to investigate the developmental potential of neural crest-derived cells that have migrated to and colonized the avian bowel. Segments of quail bowel (removed at E4) were grafted between the somites and neural tube of younger (E2) chick host embryos. Grafts were placed at a truncal level, adjacent to somites 14-24. Initial experiments, done in vitro, confirmed that crest-derived cells are capable of migrating out of segments of foregut explanted at E4. The foregut, which at E4 has been colonized by cells derived from the vagal crest, served as the donor tissue. Comparative observations were made following grafts of control tissues, which included hindgut, lung primordia, mesonephros and limb bud. Additional experiments were done with chimeric bowel in which only the crest-derived cells were of quail origin. Targets in the host embryos colonized by crest-derived cells from the foregut grafts included the neural tube, spinal roots and ganglia, peripheral nerves, sympathetic ganglia and the adrenals, but not the gut. Donor cells in these target organs were immunostained by the monoclonal antibody, NC-1, indicating that they were crest-derived and developing along neural or glial lineages. Some of the crest-derived cells (NC-1-immunoreactive) that left the bowel and reached sympathetic ganglia, but not peripheral nerves or dorsal root ganglia, co-expressed tyrosine hydroxylase immunoreactivity, a neural characteristic never expressed by crest-derived cells in the avian gut. None of the cells leaving enteric back-grafts produced pigment. Cells of mesodermal origin were also found to leave donor explants and aggregate in dermis and feather germs near the grafts. These observations indicate that crest-derived cells, having previously migrated to the bowel, retain the ability to migrate to distant sites in a younger embryo. The routes taken by these cells appear to reflect, not their previous migratory experience, but the level of the host embryo into which the graft is placed. Some of the population of crest-derived cells that leave the back-transplanted gut remain capable of expressing phenotypes that they do not express within the bowel in situ, but which are appropriate for the site in the host embryo to which they migrate.     

Rat-liver superoxide dismutase. Purification and age-related modifications.

Cytoplasmic superoxide dismutase has been purified from livers of young (6 months) and old (27 months) rats. The enzyme purified from old animals shows an age-related reduction in the specific activity, accumulation of antigenically cross-reacting material and increased sensitivity to temperature. No differences were found in the molecular weight, electrophoretic mobility, antigenicity and Ki between enzymes purified from young and old rats. This is the first demonstration of age-related alterations in a purified form of a non-metabolic enzyme, which can be related to reduced activity. The possible role of this reduced activity in age-dependent deterioration of cellular functions is discussed.     

Role of Ly-1:Qa1- and Ly-1:Qa1+ inducer T cells in activation of Ly-23 effectors of suppression of antibody production in mice

Ly-2+ effectors of T cell-mediated suppression require inducing signals from antigen and a helper cell bearing the Ly-1+:Qa1+ surface phenotype. In this report, we have further examined the helper cell requirements for suppressor cell induction of antibody production in mice. By using the T cell subset education procedure in vitro, we have activated T cells to sheep red blood cells (SRBC) antigens and then purified Ly-2 cells before testing for suppressor activity in assay cultures of defined T and B cell subsets. We have confirmed our previous observations that Ly-1+:Qa1+ cells are required for activation of T suppressors, but have found that under the appropriate conditions, there is not a strict requirement for the Ly-123 subset of T cells. Furthermore, if Ly-23 cells are stimulated in the presence of Ly-1+:Qa1- T cells, effective suppressors can be obtained only if a source of Ly-1:Qa1+ inducers is added to the assay culture. If Ly-23 cells are activated by antigen in the absence of Ly-1 cells, subsequent exposure to the Ly-1+:Qa1+ subset under the conditions tested here is not sufficient to activate suppressors. These results show that effectors of suppression, like B cells and cytotoxic T lymphocytes, may respond to two helper cells.     

Purification and characterization of TNP-specific immunoregulatory molecules produced by T cells sensitized by picrylchloride (PC1F)

T cell-derived TNP-specific factors associated with immunoregulatory activity were obtained by culture of T cells obtained from mice sensitized by skin-painting with picrylchloride. Culture medium was absorbed to TNP-Sepharose and TNP binding proteins were prepared by elution with TNP. The hapten affinity-purified proteins were characterized by size and charge and were found to be acidic 70,000 m.w. polypeptides that occur as monomers or oligomers. Oligomeric proteins interact with factors produced by mice injected with trinitrobenzenesulfonic acid to form factors that suppress specifically the ability of TNP-sensitized T cells to transfer contact sensitivity to TNP. Monomeric (no more than 70,000 m.w.) molecules do not form suppressor factors but can transfer contact sensitivity to TNP. Moreover, reduction and alkylation of oligomeric molecules inactivates their suppressor activity but causes them to be able to transfer contact sensitivity. The results suggest that T cell-derived antigen-specific molecules may have different effector functions dependent on their oligomeric state.