Expression of LFA‐1 by a lymphoblastoid cell line from a patient with monosomy 21: effects on intercellular adhesion

SUMMARY Monosomy 21 (M21) is a rare aneuploid condition which in certain cases leads to reduced levels of chromosome 21 gene products. We have prepared an Epstein‐Barr virus lymphoblastoid cell‐line (LCL) from patient with M21 who has immunological abnormalities, and analysed the expression of lymphocyte function‐associated antigen‐1 (LFA‐1). This heterodimeric leucocyte integrin consists of CD11a (α) subunits non‐covalently associated with CD 18 (β) subunits coded, respectively, by genes on chromosomes 16 and 21. To determine whether monosomy 21 results in decreased expression of LFA‐1, monoclonal antibodies were used to compare the expression of CD 1 la and CD18 on the M21 LCL with LCL from trisomy 21 (Down's syndrome, T21), normal controls and a possible case of leucocyte adhesion deficiency. In addition, phorbol‐ester‐induced homotypic adhesion, an LFA‐1‐mediated effect, was compared in these LCLs. The results are consistent with a gene dosage mediated reduction of LFA‐1 expression by the M21 LCL.