Infection of mod-1(ok103), ser-1(ok345), ser-7(tm1325), ser-7(ok1944), ser-4(ok512) mutants and ser-1(ok345);ser-7(tm13325) double mutants indicates that at least two GPCRs (SER-1 and SER-7) are required for serotonin effects on the immune response (Figure S5). Here, CBX1 is linked to infection.