Coordinate induction of Ia alpha, beta, and Ii mRNA in a macrophage cell line.

We demonstrated a tightly coordinated timing in the appearance of mRNA for the four class II (Ia) MHC chains, A alpha, A beta, E alpha, and E beta, and the Ia-associated invariant chain in a murine macrophage cell line after the addition of immune interferon (IFN-gamma) or of IFN-gamma-containing supernatants from Con A-stimulated spleen cells. The marked increase in mRNA levels for these molecules at approximately 8 hr after IFN-gamma addition contrasts sharply with the earlier, more gradual kinetics observed for class I (H-2) and beta 2-microglobulin mRNA. The difference in kinetics of IFN-gamma induction of class I and class II mRNA suggests differential regulation of the expression of Ia and H-2 antigens. The long lag period preceding detection of Ia mRNA raises the possibility that IFN-gamma may not directly mediate the increase in mRNA expression, but may act through an additional cellular intermediate.