1. R2 population increased from 18 to 72 h after infection. Only R1 was detected in naive. 2. C3, C4b, C3ar1, and C5ar1 mRNAs were significantly upregulated. 3. C3 was detected at significantly higher levels in R2 compared to R1 cells. (4) Other immune regulators, such as cytokines and MHC I and II genes, were also upregulated. The gene discussed is C3AR1; the disease is infection.