AbstractWe have studied the tissue distribution of interleukin (IL) and hemopoietic colony‐stimulating factor (CSF) transcripts in mice by S1‐nuclease protection analysis. Accumulation of several of these mRNAs in response to intravenous injection of lipopolysaccharide (IPS) appears to occur in a tissue‐specific fashion. IL‐1α transcripts accumulate in spleen and lung; IL‐6 transcripts accumulate in kidney, heart, and spleen; granulocyte‐macrophage‐CSF transcripts accumulate in lung and heart; and granulocyte‐CSF transcripts accumulate in heart. Three distinct patterns of in vivo mRNA accumulation were detected: (1) silent—interleukins 2–5 showed no transcripts in either LPS‐treated or untreated animals; (2) induced—IL‐1α, IL‐6, granulocyte‐macrophage (GM)‐CSF, and G‐CSF transcripts were increased in abundance in LPS‐injected mice; and (3) constitutive—M‐CSF transcripts were found in similar amounts in both untreated and treated mice