The following inbred strains are homozygous for the recessive QTL, Micrl, and do not respond to microwave exposure by increasing splenic C3 receptor-bearing B cells: A/J, BALB/cJ, C3HeB/FeN, C57BL/6J, C57BL/10J (inferred from the response of two congenic lines "B10.BR", "B10.D2", "B10.D2"), C58/J, AK.B6-H2b, and B6.AK-H2k. These recombinant inbred strains are also non-responding: BXH2/Ty, BXH6/Ty, BXH7/Ty, BXH12/Ty, and BXH14/Ty.