CHARACTERIZATION OF LYMPHOCYTE FUNCTION-ASSOCIATED ANTIGEN-1 (LFA-1)-DEFICIENT T-CELL LINES - THE ALPHA(L) AND BETA(2) SUBUNITS ARE INTERDEPENDENT FOR CELL-SURFACE EXPRESSION

The leukocyte, or beta(2), integrins are heterodimeric cell surface mo lecules that share a common beta subunit, and have unique alpha subuni ts, LFA-1 is the predominant beta(2) integrin on lymphocytes, and play s an important role in many lymphocyte functions; however, most studie s of the cytoplasmic regions of LFA-1 have been performed in transfect ed epithelial cells, such as COS, in part because no lymphoid cell lin es deficient in the LFA-1 alpha subunit have been described. To addres s structure-function studies of beta(2) integrins in relevant cell typ es, two T lymphoblastoid cell clones that completely lack cell surface LFA-1, J-beta(2).7 and SK-beta(2).7, derived from Jurkat and SKW3, re spectively, were prepared by chemical mutagenesis and selection. Biosy nthetic labeling and immunoprecipitation showed that the J-beta(2).7 c lone did not translate any LFA-1 alpha subunit protein, while the SK-b eta(2).7 cells did not synthesize any beta(2) subunit protein. Norther n blot analysis of poly(A(+)) RNA from these cells revealed an absence of the corresponding mRNA in each case. By transfection analysis, onl y the a subunit reconstituted LFA-1 expression in the J-beta(2).7 cell s, while only the beta subunit restored cell surface LFA-1 expression in the SK-beta(2).7 cells. Functional studies with the parental cell l ines, the J-beta(2).7 and SK-beta(2).7 cells, and the transfectants sh owed that all binding of Jurkat and SKW3 cells to purified ICAM-1 is m ediated by LFA-1, and the reconstituted LFA-1 expressed by the J-beta( 2).7 and SK-beta(2).7 transfected cells is regulated normally.