The Effect of X-rays on the Precursors of Antibody Forming Cells (B Cells) as Measured with the in Vitro Limiting Dilution Assay

Summary The effect of X-irradiation upon murine antibody-forming cell precursors (B cells) was established in cultures of spleen cells stimulated with the B cell mitogen lipopolysaccharide (LPS). At day 5 and 7 the numbers of IgM- and IgG2-secreting cells were determined in cultures of irradiated and nonirradiated spleen cells. From these numbers a Do of 0·6 - 1·2 Gy for the IgM, and of 0·9 - 2·1 Gy for the IgG2 response was calculated. Similar Do values were obtained under limiting dilution culture conditions. In the limiting dilution assay the effect of irradiation upon the size of the IgM-producing clones could also be determined. It was found that irradiation reduced the number of LPS-reactive B cells without affecting the size of the clones produced by the surviving cells.