IL-7 promotes thymocyte proliferation and maintains immunocompetent thymocytes bearing alpha beta or gamma delta T-cell receptors in vitro: synergism with IL-2

IL-7 induced the proliferation of normal thymocytes and the effect was synergistically potentiated by a small dose of IL-2, which by itself hardly affected thymocyte proliferation. No synergism was observed between IL-7 and any one of the other lymphokines including IL-1, IL-3, and IL-4. The thymocyte culture stimulated with IL-7 and IL-2 consisted of single positive (CD4+CD8- and CD4-CD8+) and double negative (CD4-CD8-) populations, and double positive (CD4+CD8+) cells were completely deleted. Both single positive and double negative thymocytes expressed CD3, but only the former exhibited V beta 8 and V beta 6 in an expected proportion (approximately 30% in BALB/c mice) and the latter none at all. Immunoprecipitation of the cultured thymocytes by anti-TCR gamma antibody, on the other hand, revealed the presence of a TCR gamma chain. Taken together, these results indicated that the thymocyte cultured with IL-7 and IL-2 consisted of mature T cells bearing alpha beta or gamma delta TCR. Experiments using preselected thymocyte subpopulations indicated that double negative cells responded to both IL-7 and IL-2 with positive synergism when combined, while thymocytes enriched for single positive cells preferentially responded to IL-7 with little response to IL-2 and no detectable synergism. Double positive thymocytes showed no proliferation in response to IL-7 and IL-2. In contrast to single positive thymocytes, splenic T cells hardly responded to IL-7, although significant proliferation was induced in the presence of a low dose of IL-2. Thymocytes cultured with IL-7 and IL-2 showed little nonspecific cytotoxic activity, but responded to Con A or alloantigen, whereas those stimulated with a high dose of IL-2 alone exhibited potent cytotoxic activity. These results indicated that IL-7 was involved in the generation of immunocompetent T cells in the thymus in concert with IL-2.     

Poly(adenosine diphosphate ribose) polymerase activity in neuronal and glial nuclei from bovine cerebrum

Two different preparations isolated from beef cerebrum have been used to compare the polyadenosine diphosphate ribose (polyADPR) polymerase activities in neuronal and glial nuclei: (1) nuclear suspensions (with or without DNase I treatment), and (2) 1 M NaCl nuclear extracts (soluble enzyme). The DNAse I treatment of nuclei and the solubilization of polyADPR polymerase by 1 M NaCl enhances the polyADPR polymerase activity. The polyADPR polymerase activity is similar in neuronal and glial nuclear suspensions, while the neuronal soluble enzyme activity is significantly higher than that of the glial soluble enzyme. Evidence is presented that the difference in soluble enzyme activities is not due to the effects of DNA or degrading enzymes. Some activating factor(s) seem to be present in neuronal soluble extracts, while both inhibiting and activating factor(s) seem to be present in glial soluble extracts.     

Location of Lyb-2 on mouse chromosome 4

TheLyb-2 locus responsible for the B-lymphocyte alloantigen system Lyb-2 is located on chromosome 4 at a distance of 20.6±4.9 map units fromPgm-2. A three-point cross indicated the orderLyb-2: Mup-1b Pgm-2.