Cell lineage differentiation cytokine functions

Cells of the T cell lineage appear to be more sensitive to the immunomodulatory effects of Pb compared to other lymphoid populations. In addition, there are considerable differences in sensitivity across various T cell subpopulations [38 41], This differential sensitivity has become another major hallmark of Pb-induced immunotoxicity, although most data implicate T cells as indirect targets of Pb immunotoxicity. Both in vivo and in vitro observations of T-dependent immune responses in the presence of Pb suggest that T helper function and Th-dependent cytokines are skewed preferentially toward Th2 reactivities. Smith and Lawrence [42] found that Pb inhibited antigen presentation and stimulated a T cell clone of the Thl phenotype. McCabe and Lawrence [38] were the first to show that Pb inhibited Thl stimulation while it promoted presentation to Th2 clones. Heo and colleagues [39 41] provided both in vitro and in vivo results supporting this immunomodulation by Pb. 

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