LFA‐1 β‐chain synthesis and degradation in patients with leukocyte‐adhesive proteins deficiency

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Abstract
The defective membrane expression of the adhesive protein family (LFA-1, Mo1 and p 150, 93) on leukocytes from certain patients with recurrent bacterial infections was shown to be secondary to the absence of synthesis of mature β chain that is common to all three antigens (Springer et al., 1984, Lisowska-Grospierre et al. 1986). In all patients, studies of β-chain biosynthesis that lead to this conclusion were performed using the monoclonal anti-β chain antibody to isolate the β subunit. Since this antibody detects the mature form of β chainonly, the potential presence of a precursor or of an abnormal β chain in the patient's cells could not be tested. the availability of the polyclonal antibody to the purified β subunit allowed us t re-examine the biosynthesis of the LFA-1 subunits in 3 affected children. In al 3 patients, the absence of membrane expression of the LFA-1, CR3 and p150,95 proteins was confirmed. The LFA-1 α-chain precursor of 170 kDa was detected in the lysates of PHA blasts of two children, but was not detected in the third. The β-chain precursor of 85 kDa was isolated by the polyclonal anti-β chain antiserum from the cytoplasm of phytohemagglutinin and Epstein-Barr virus-induced blasts of one patient. The same antibody precipitated some peptides of smaller mol. wt. from the cell lysates of 2 other patients. These results suggest that in this disorder the membrane nonexpression of the adhesive proteins is probably due to the structural abnormality of β chain which, although synthesized, is rapidly degradated.

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