Differential expression of the LFA-1 molecule on the human peripheral blood mononuclear cell subpopulations

The expression of leukocyte function associated antigen 1 (LFA-1) was studied on human peripheral blood mononuclear cells (PBMNC) by a double immunofluorescence method. Monoclonal antibodies IOT18 (recognizing the beta chain, 95 kDa, CD18) and SPVL7 (recognizing the alpha chain, 180 kDa, CD11a) were used. These antibodies revealed the same heterogeneous distribution of the LFA-1 molecule among peripheral blood mononuclear cells. A bimodal profile characterized the lymphocytes, whereas the monocyte subpopulation presented a unimodal profile. NK cells, including CD16, CD8 dim, expressed the LFA-1 with a high density. B cells expressing the CD19 phenotype showed surface LFA-1 at a low level, whereas it appeared with an intermediate intensity on the T helpers/inducers (CD4 cells). Among the cytotoxic cells (CD8) and the immunoregulatory subpopulations associated with an immunosuppressive response (CD8+ CD11b+, CD8+ CD11b- and CD8+ leu8+) or with a contrasuppressive response (Vicia villosa cells), an heterogeneous LFA-1 expression was observed, discriminating the LFA-1 dim and the LFA-1 bright cells. Anti LFA-1 antibodies also allowed us to define three novel subsets among the CD8 cells: the CD8 dim LFA-1 bright, the CD8 bright LFA-1 bright, and the CD8 bright LFA-1 dim cell subpopulations. This heterogeneous distribution of LFA-1 among PBMNC may be associated with different functions of the different cell subsets analyzed in this study.