Somatic cell hybrid clones were isolated from the fusion of RPC 5,4 mouse myeloma cells and B lymphocytes from three patients with agammaglobulinemia. One patient had X-linked agammaglobulinemia; the remaining two patients had common varied agammaglobulinemia. All three patients had B lymphocytes which fail to secrete immunoglobulin. The hybrid nature of the clones was established by examinatio...