MICA, a new polymorphic HLA-related antigen, is expressed mainly by keratinocytes, endothelial cells and monocytes

ZWIRNER, NORBERTO WALTER; FERNÁNDEZ-VIÑA, MARCELO; STASTNY, PETER

IMMUNOGENETICS

Springer

Lugar: Berlin/Heidelberg, Alemania; Año: 1997 vol. 47 p. 139 - 148

0093-7711

MICA is a new polymorphic gene in the HLA region expressed in epithelial cell lines and gastrointestinal epithelium. Little is yet known about the MICA protein, and the pattern of its expression by freshly isolated cells has not been established. In the present experiments, we used antibodies raised in rabbits against a1 and a2 domainpeptides to study the expression of MICA. By western blot and immunoprecipitation, we detected a band of 62 000 Mr in various cell lines (THP-1, U937, HeLa, A431, Raji, MOLT-4, and HUV-EC-C) and in freshly isolated keratinocytes, endothelial cells, and monocytes but not in CD4+ and CD8+ T cells, and CD19+ cells (B lymphocytes). It was not possible to up-regulate the expression of MICA in different cells by stimulation with g-interferon, but the expression of MICA was induced in phytohemagglutinin-stimulated T cells. We confirmed that MICA is expressed at the cell surface by flow cytometry. Results of immunoprecipitation studies of b2-microglobulin(b2m)- or MICA-depleted, metabolically labeled HeLa cells indicated that MICA was not associated with b2m. Although the function of MICA is still unknown, its restricted pattern of tissue expression, the fact that it is expressed on the cell surface, and its polymorphic nature suggest that this new molecule, encoded close to HLA class I, may play a role in the interaction between epithelial cells and cells of the immune system