Bovine CD18 is necessary and sufficient to mediate Mannheimia (Pasteurella) haemolytica leukotoxin-induced cytolysis

Leukotoxin (Lkt) secreted by Mannheimia (Pasteurella) haemolytica is an RTX toxin which is specific for ruminant leukocytes. Lkt binds to beta(2) integrins on the surface of bovine leukocytes. beta(2) integrins have a common beta subunit, CD18, that associates with three distinct alpha chains, CD11a, CD11b, and CD11c, to give rise to three different beta(2) integrins, CD11a/CD18 (LFA-1), CD11b/CD18 (Mac-1), and CD11c/CD18 (CR4), respectively. Our earlier studies revealed that Lkt binds to all three beta(2) integrins, suggesting that the common beta subunit, CD18, may be the receptor for Lkt. In order to unequivocally elucidate the role of bovine CD18 as a receptor for Lkt, a murine cell line nonsusceptible to Lkt (P815) was transfected with cDNA for bovine CD18. One of the transfectants, 2B2, stably expressed bovine CD18 on the cell surface. The 2B2 transfectant was effectively lysed by Lkt in a concentration-dependent manner, whereas the P815 parent cells were not. Immunoprecipitation of cell surface proteins of 2B2 with monoclonal antibodies specific for bovine CD18 or murine CD11a suggested that bovine CD18 was expressed on the cell surface of 2B2 as a heterodimer with murine CD11a. Expression of bovine CD18 and the Lkt-induced cytotoxicity of 2B2 cells were compared with those of bovine polymorphonuclear neutrophils and lymphocytes. There was a strong correlation between cell surface expression of bovine CD18 and percent cytotoxicity induced by Lkt. These results indicate that bovine CD18 is necessary and sufficient to mediate Lkt-induced cytolysis of target cells.     

Alteration of cytokine production in follicular cystic ovaries induced in mice by neonatal estradiol injection

PROBLEM: Neonatal estradiol injections in mice lead to follicular cystic ovaries that are similar to ovaries in patients with polycystic ovarian syndrome (PCOS). The present study examined ovarian cytokine production following neonatal estradiol injection. METHOD OF STUDY: Female (C3H,HeJ x 129/HeJ)F1 mice were injected daily with 20 microg 17beta-estradiol from 0-3 days postpartum. At intervals, animals were sacrificed to determine ovarian architecture, circulating levels of estradiol, ovarian and peritoneal macrophage cytokine production, and ovarian P450 aromatase enzyme mRNA levels. RESULTS: Similar to PCOS, our results show that neonatally estradiol-injected mice have lower levels of circulating estrogen that are correlated with decreased mRNA levels of P450 aromatase enzyme. Our data also show that follicular cystic ovaries have increased tumor necrosis factor (TNF)-alpha and interleukin (IL)-6 production. This increase in TNF-alpha and IL-6 production is also observed in peritoneal macrophages of estradiol-injected mice. CONCLUSION: The present study showed that neonatal estrogen injection in mice has an overall systemic effect on cytokine production. We speculate that increased cytokine production may alter certain important steps in follicular maturation, ultimately contributing to ovarian dysfunction.     

The CTLA-4 gene region of chromosome 2q33 is linked to, and associated with, type 1 diabetes. Belgian Diabetes Registry

Susceptibility to autoimmune insulin-dependent (type 1) diabetes mellitus is determined by a combination of environmental and genetic factors, which include variation in MHC genes on chromosome 6p21 (IDDM1) and the insulin gene on chromosome 11p15 (IDDM2). However, linkage to IDDM1 and IDDM2 cannot explain the clustering of type 1 diabetes in families, and a role for other genes is inferred. In the present report we describe linkage and association of type 1 diabetes to the CTLA-4 gene (cytotoxic T lymphocyte associated-4) on chromosome 2q33 (designated IDDM12). CTLA-4 is a strong candidate gene for T cell- mediated autoimmune disease because it encodes a T cell receptor that mediates T cell apoptosis and is a vital negative regulator of T cell activation. In addition, we provide supporting evidence that CTLA-4 is associated with susceptibility to Graves' disease, another organ- specific autoimmune disease.      

Altered airway responsiveness in CD38-deficient mice

Cyclic ADP-ribose (cADPR) mobilizes calcium from intracellular stores and contributes to agonist-induced intracellular calcium elevation in airway smooth muscle (ASM). In this study we determined the functional role of CD38/cADPR signaling in the regulation of airway tone using CD38 deficient (cd38(-/-)) mice. The responsiveness to different doses of methacholine, as determined by changes in lung resistance and dynamic compliance, was significantly (P < or = 0.05) lower in cd38(-/-) mice compared with wild-type controls. To determine the mechanism responsible for the reduced responsiveness, we measured the intracellular calcium responses to contractile agonists in ASM cells. In ASM cells isolated from cd38(-/-) mice, the intracellular calcium responses to acetylcholine and endothelin-1 were significantly lower than in controls. Pretreatment of ASM cells with a cADPR antagonist resulted in attenuated intracellular calcium responses to endothelin-1 in cells isolated from wild-type mice, but not in those isolated from the cd38(-/-) mice. Very low cADPR levels and no detectable ADP-ribosyl cyclase activity were observed in lung tissue from cd38(-/-) mice, suggesting that CD38 is a critical source for cADPR synthesis. The results of the present study demonstrate that CD38/cADPR contributes to airway smooth muscle tone and responsiveness through its effects on agonist-induced elevation of intracellular calcium in ASM cells.     

Angiodysplasia of cardia of stomach--a case report

Angiodysplasia of gastrointestinal tract is still thought to be an entity of unknown aetiology. This lesion is most commonly observed in elderly patients presenting with severe and persistent iron deficiency anaemia, following occult blood loss or acute episodes of haematemesis. In the stomach antral vascular ectasia is the most common presentation. We report an autopsy case of vascular ectasia in the cardia of stomach in a young patient with clinical symptoms of anaemia as the presentation and an associated secondary hemosiderosis of liver.