To determine whether or not the T lymphocyte-dependent mitogens Concanavalin A (Con A) and Phytohemagglutinin (PHA) and the B lymphocyte-dependent mitogens pokeweed mitogen (PWM) and Escherichia coli lipopolysaccharide (LPS) elicit fundamentally different patterns of responsiveness by mixed cell populations, we studied unmanipulated murine spleen cell populations in cultures free of exogenous serum. Advantage was taken of genetically determined differences in Con A- and PHA-stimulated responses of spleen cells from mice in F2 populations with (BALB/c × B10.D2)F2 animals (all H-2d homozygotes) being used in order to control for possible ongoing H-linked Ir gene-dependent immune responses. That is, broad genetically determined variability in T-dependent mitogen response was utilized in order to evaluate the correlations among spontaneous DNA synthesis and that stimulated by the four mitogens, Con A, PHA, PWM, and LPS. Spontaneous DNA synthesis when no mitogen was added to the cultures was significantly correlated with the LPS-stimulated response (r = 0.659, p < 0.005). The PWM response also showed a slight positive correlation with the no mitogen response (r = 0.444, p < 0.05), but Con A and PHA responses were not correlated with the level of spontaneous DNA synthesis. Con A and PHA responses were highly correlated with each other (r = 0.812, p < 0.001) as were LPS and PWM responses (r = 0.806, p < 0.001). There was some positive correlation between Con A and LPS responses (r = 0.603, p < 0.005), whereas the PHA response was not correlated with any response other than that to Con A. These data support the concept that there is an exogenous serum independent, fundamental difference in the response to the T lymphocyte-dependent mitogens Con A and PHA compared to the response to the B lymphocyte-dependent mitogens PWM and LPS.

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