Spleens of both the resistant and sensitive lines did not express leptin mRNA and lowly expressed LEPR mRNA, regardless of infection by MDV, while mRNAs of TNF and TNFR1 were induced in the spleens of both sensitive and resistant lines (TNF, 10- and 3-fold; TNFR1, 2- and 1.5-fold, respectively). The gene discussed is TNF; the disease is infection.