Development of thymic lymphomas in mice disrupted of Brca2 allele in the thymus

Germ-line mutations in BRCA2 predispose to early-onset cancer. Homozygous mutant mouse, which has Brca2 truncated in exon 11 exhibit paradoxic occurrence of growth retardation and development of thymic lymphomas. However, due to its large embryonic lethality, cohort studies on the thymic lymphomas were not feasible. With the aid of Cre-loxP system, we demonstrate here that thymus-specific disruption of Brca2 allele without crossing it to p53-mutant background leads to the development of thymic lymphomas. Varying from 16 weeks to 66 weeks after birth, 25% of mice disrupted of Brca2 in the thymus died of thymic lymphomas, whereas previous report did not observe lymphomagenesis using similar Cre-loxP system. Future analysis of thymic lymphomas from these mice presented here will provide information on the cooperative mutations that are required for the BRCA2-associated pathogenesis of cancer.

Der f 2 activates phospholipase D in human T lymphocytes from Dermatophagoides farinae specific allergic individuals: Involvement of protein kinase C-alpha

The major house-dust mite allergen, Der f 2, stimulates the phospholipase D (PLD) in T lymphocytes from Dermatophagoides farinae specific allergic individuals. PLD activity increased more than two-fold in T cells from allergic patients compared with those cells from normal controls with maximal responses within 30 min after exposure of Der f 2. A well-known PLD activator PKC-alpha was found to be translocated to membrane from cytosol in Der f 2-treated T cells from Dermatophagoides farinae specific allergic individuals. Down-regulation of PKC-alpha with phorbol myristate acetate pretreatment for 24 h abolished Der f 2-induced PLD activation. Ro 320432, PKC inhibitor also reduced the effects of Der f 2-induced PLD activation suggesting that PKC-alpha acts as upstream activator of PLD in Der f 2-treated T cells. Taken together, the present data suggest that Der f 2 can stimulate PLD activity through the PKC-alpha activation in T cells from Dermatophagoides farinae allergic individuals

Cell-mediated immunosuppression in mice by street rabies virus not restored by calcium ionophore or PMA.

It is known that rabies virus can suppress the host immune system. In this study we demonstrate a depression of cell-mediated immunity in mice, peripherally infected with Thai street rabies virus. The cell-mediated cytolysis of spleen cells from mice increased transiently on day 5 after infection and declined rapidly thereafter until death. The proliferation of spleen cells stimulated with a T-cell mitogen such as phytohemagglutinin or concanavalin A, was significantly suppressed during the course of infection. There was also a marked suppression of IL-2 secretion in parallel with a decrease of the T-cell proliferative response to mitogen. The suppression of T-cell proliferation was not restored by treatment with a calcium ionophore (A 23187) or phorbol 12-myristate-13 acetate (PMA).