Cloning and evidence of an alternatively spliced isoform of lymphocyte function associated antigen - one

Lymphocyte associated function - one integrin (LFA-1 - CD18/CD11a) is an adhesion molecule which is expressed in cells of leukocyte origin. Antibodies against LFA-1 are known to block T cell responses to antigen presenting cells, T cell help to B cells, NK mediated killing, macrophage killing of tumor cells, and leukocyte endothelium adhesion/extravasation. In this study, the presence of an alternatively spliced isoform of LFA-1 (designated as LFA-1 minor) was demonstrated in T cells, B cells and monocytes. A 114 bp deletion was identified at the extracellular region of CD11a (αL), which is very close to the transmembrane domain of LFA-1. Computer analysis showed that the deleted region contains a casein II kinase phosphorylation site. Northern blot analysis indicated the possibility of several other alternatively spliced transcripts of CD11a. Further experiments showed that the expression of the alternatively spliced isoform of CD11a was modulated by the mitogens like Con-A, LPS, and PMA. It is suggested that the alternatively spliced isoform may have different binding affinity and/or signalling properties and may play an important role in the regulation of the function of LFA-A.