CD4 and systemic inflammatory response syndrome: Importantly and irrespective of the numerical values, a prior episode of SIRS or sepsis did not alter antigen responses of Ag-specific effector CD4+ T-cells on a per cell basis as the mean level of IFNγ production (plotted as geometric mean fluorescence index (gMFI)) in GP61-stimulated CD4+ T-cells was unaltered in all groups (Fig. 4B).