Characterization of mouse thoracic duct B lymphocytes. I. Evidence of functional heterogeneity.

Thoracic duct lymphocytes (TDL) from C3H/Tif and BALB/c mice were studied for their in vitro reactivity to the B cell mitogens lipopolysaccharide (LPS) and lipoprotein (LP). Roughly 4% and 10% of the surface immunoglobulin (Ig)-positive cells in these populations could be stimulated by LPS and LP, respectively, to generate clones of IgM-secreting cells. Among LPS-reactive B cells, roughly 30% developed into clones which also produced IgG3 or IgG2, while only a very small fraction (1-2%) of all precursors could give rise to clones secreting IgG1 and IgA. Freshly collected TDL from some batches of C3H/HeJ mice displayed a high proportion of Ig-containing B cell blasts (5-10%), which did not secrete enough Ig to be detected as plaque-forming cells (PFC). These cells, however, under appropriate culture conditions and stimulated by LP (but not by Nocardia mitogen), differentiated to PFC of the various Ig classes without dividing.