Pre-B cells in bone marrow: peanut agglutinin binding and separation of cytoplasmic mu chain-bearing cell populations in normal, post-irradiation and polycythemic mice using fluorescence-activated cell sorting.

Mouse bone marrow cells exposed to fluorescein-conjugated peanut agglutinin (PNA) showed subsets of highly labeled cells when analyzed in a fluorescence-activated cell sorter. After separating three cell fractions of large and small PNA-binding cells and PNA-nonbinding cells, respectively, the B lymphocyte precursor (pre-B) cells, having cytoplasmic mu chains (c mu) without surface mu chains (s mu), were recovered solely in the PNA-binding fractions. Only a minority of s mu+ small lymphocytes having the lowest densities of s mu bound PNA. Small and large c mu+ s mu- pre-B cell populations were separated in high degrees of purity in the PNA-binding fractions, especially when obtained from bone marrow undergoing lymphoid regeneration after sublethal X-irradiation and during stimulation of lymphocyte production in post-polycythemic erythroid suppression. Characteristic shifts in the size distribution profile of PNA-binding cells reflected changes in the maturation stage of the pre-B cells. The results demonstrate that surface membrane components with strong PNA-binding capacities characterize c mu+ s mu- pre-B cells in the bone marrow during both normal and perturbed primary B lymphocyte genesis. The PNA-binding sites become undetectable soon after the first expression of s mu. This property permits the isolation from the bone marrow of high concentrations of subsets of large and small c mu+ s mu- cells in a viable state suitable for use in further functional studies.