SOLUBLE FC-GAMMA-RECEPTOR, FC-GAMMA-RIIA2, IS PRESENT IN 2 FORMS IN HUMAN SERUM AND IS INCREASED IN PATIENTS - WITH STAGE-C CHRONIC LYMPHOCYTIC-LEUKEMIA

Human Fc gamma receptor type II (Fc gamma RII/CD32) can be produced in a soluble form, termed Fc gamma RIIa2, which contains the extra-and i ntracellular regions of the receptor, due to an alternative splicing o f the transmembrane domain-encoding exon. We show that human sera cont ain two forms of Fc gamma RIIa2. A full-length secreted protein, which has a 32 kDa backbone, can be detected only in some sera while all se ra contain a C-terminal truncated form, lacking part of the intracytop lasmic tail, and exhibiting a 24 kDa protein backbone. The 24 kDa form is significantly increased in sera from stage C patients with B chron ic lymphocytic leukemia, compared to healthy donors, stage A and B CLL patients, or CLL patients in complete remission.