Effect of benzene metabolites on phytohemagglutinin-stimulated lymphopoiesis in rat bone marrow.

Chronic exposure of animals to benzene results in lymphocytopenia and bone marrow depression. A highly sensitive microculture system was developed to amplify and characterize marrow mitogen response which depended on the isolation of cells by Percoll continuous density gradient centrifugation and strict adherence to optimal culture conditions. Maximal mitogen responses to phytohemagglutinin (PHA) and concanavalin A (con A), as assessed by (3H)-thymidine uptake, occurred at later times in rat bone marrow cultures (days 5-7 of culture) compared with spleen and thymus (days 2-3). Compared with spleen and thymus, the PHA: con A stimulation ratio was inverted for marrow, yet the responsive cells were morphologically identical to those of peripheral lymphoid organs. Populations enriched in lymphoid precursors were inhibited from responding to PHA stimulation at noncytotoxic concentration (less than microM) of the benzene metabolites, p-benzoquinone or 1, 2, 4-benzenetriol. Pretreatment with less than microM concentrations of metabolite resulted in a modulation of lectin-induced responses such the blastogenesis was induced at higher concentrations of lectin relative to untreated cells. These changes indicate that known metabolites of benzene induce a concentration dependent modulation of differentiation and proliferation in lectin-stimulated cells from rat bone marrow in vitro.