title: Protein A reactivity of lymphocytes from some patients with chronic lymphocytic leukaemia mediated by an interaction with the F(ab')2 region of surface immunoglobulin.
abstract: Peripheral blood lymphocytes (PBL) from 15 of 38 patients with chronic lymphocytic leukaemia (CLL) were capable of forming rosettes with human erythrocytes coated with staphylococcal protein A (SpA-HRBC). PBL from seven patients also showed a marked proliferative response after stimulation with Staphylococcus aureus bacteria strain Cowan I (Cowan Staph). The SpA-rosetting of CLL cells was inhibited by incubation with F(ab')2 fragments of anti-immunoglobulin (Ig) antibodies. In addition, incubation with these fragments inhibited the proliferative response of leukaemic B cells to Cowan Staph. The Cowan-Staph induced proliferation of CLL cells was also impaired by the addition of normal human IgG and human IgG F(ab')2 fragments to the cultures, whereas non-immune rabbit IgG was not inhibitory. The inhibitory activity of human IgG F(ab')2 fragments was retained by a SpA-Sepharose column, and it was found in the material recovered from the same column by acid elution. These data indicate that an interaction between SpA and a structure located in the F(ab')2 region of surface Ig of different classes is responsible for either SpA-binding or the Cowan-Staph-induced proliferative response of PBL from some patients with CLL.
mesh_terms: D000818:Animals; D000888:Antibodies, Anti-Idiotypic; D006801:Humans; D007140:Immunoglobulin Fab Fragments; D007074:Immunoglobulin G; D066298:In Vitro Techniques; D007945:Leukemia, Lymphoid / Q000276:immunology*; D008213:Lymphocyte Activation; D011817:Rabbits; D011947:Receptors, Antigen, B-Cell; D012397:Rosette Formation; D013205:Staphylococcal Protein A / Q000276:immunology*
chemical_list: D000888:Antibodies, Anti-Idiotypic; D007140:Immunoglobulin Fab Fragments; D007074:Immunoglobulin G; D011947:Receptors, Antigen, B-Cell; D013205:Staphylococcal Protein A