Globotriaosylceramide (Gb(3)/CD77) is synthesized and surface expressed bybovine lymphocytes upon activation in vitro

Neutral glycosphingolipids (GSLs) are considered activation markers on huma n lymphocytes, which are fundamental for studying the immune system. For ca ttle, only a limited number of activation markers has yet been identified. We recently showed that Shiga toxin 1, known to use globotriaosylceramide ( Gb(3) syn. CD77) as a cellular receptor, depresses proliferation of activat ed bovine lymphocytes [Infect. Immunol. 67 (1999b) 2209]. In order to confi rm the expression Of Gb(3)/CD77 on bovine lymphocytes, we flowcytometricall y examined a bovine B-lymphoma cell line (BL-3) and bovine peripheral blood mononuclear cells (PBMC) before and after mitogenic stimulation and bioche mically characterized neutral GSLs extracted from PBMC. CD77 was detected o n the surface of BL-3 cells and cultured PBMC essentially after mitogenic s timulation. Although expressed by all PBMC subpopulations identified, the p ortion of CD77(+) cells was highest for BoCD8(+) cells, followed by B-cells and BoCD4(+) cells at day 4 of cultivation. Ceramide trihexoside of stimul ated PBMC was structurally determined as Gal(alpha1-4)GaI(1-4)Glc(1-1)ceram ide (Gb3). Biochemically, Gb(3) was also detected within unstimulated PBMC which contained ceramide monohexoside (CMH) and Gb(3) in a ratio of about 4 : 1, However, stimulation induced an increase of CMH and Gb(3) by a factor of 2.5 and 10, respectively, implicating that bovine lymphocytes regulate s urface expression of Gb(3)/CD77 predominantly by quantitative changes in th e Gb(3) metabolism. This report presents Gb(3)/CD77 as the first GSL identi fied on bovine immune cells and highly recommends this activation dependent antigen as a useful tool to investigate lymphocyte activation within the b ovine immune system. (C) 2001 Elsevier Science B.V. All rights reserved.