ABNORMAL ASSOCIATION BETWEEN INVARIANT CHAIN AND HLA CLASS-II ALPHA-CHAIN AND BETA-CHAIN IN CHRONIC LYMPHOCYTIC-LEUKEMIA

We have previously shown that peripheral blood lymphocytes from patien ts with chronic lymphocytic leukemia (CLL) express increased amounts o f the minor p35 form of class II invariant chain (Ii) relative to the major p33 form. In this report we demonstrate in Western blots that in CLL lymphocytes, but not in normal or Epstein-Barr virus-transformed normal lymphocytes, p35 and p33 Ii form sodium dodecyl sulfate (SDS)-r esistant complexes with class II alpha and beta chains and that these complexes form an abnormally large proportion of the total class II mo lecules. Others have shown that stable SDS-resistant alpha-beta comple xes are only formed upon binding of exogenous antigenic peptides for p resentation at the cell surface. Large amounts of p35 Ii remaining in the endoplasmic reticulum and capable of forming stable complexes with cu and beta chains could compete with endogenous antigenic peptides f or available class II peptide binding sites, The presentation of endog enous tumor antigens would thus be prevented, leading to the escape of the CLL clone from immunological surveillance. (C) 1996 Academic Pres s, Inc.