B-lymphocytosis factor in human plasma

Patients with acute thermal burns experience an increase of serum immunoglobulins associated with marked B-lymphocytosis during the recovery phase from the burn injury. This study was performed to delineate humoral factors which may induce the B-lymphocytosis in such patients. Plasma samples were obtained serially from 14 adult patients and 14 adult controls. One-half ml of plasma was injected intraperitoneally into C3H/He male mice, and absolute numbers of surface immunoglobulin-bearing cells in the mouse peripheral blood were counted. Fractionation of plasma samples was performed. The biologically active plasma fraction, tentatively termed B-lymphocytosis factor (BLF), was cultured with normal human peripheral blood lymphocytes to determine in vitro lymphocyte transformation. The solubility of 125I-labelled BLF in various organic solvents was examined. Plasma obtained from burned patients induced a marked increase of IgG, IgA, and IgM-bearing cells in the peripheral blood of mice within 3 hours after injection. The B-lymphocytosis activity of normal plasma was not significant. The molecular weight of BLF was estimated to be close to that of ribonuclease A (M.W. 13,400). Transformation of normal human peripheral blood lymphocytes was observed when cultured with BLF. 125I-labelled BLF was not soluble in organic solvents. These data suggest that BLF is not a lipopolysaccharide, and plays a role in regulation of B-lymphocyte levels in burned patients.