Thymus weight is reduced in compound H1 knockout mice. Thymi from mice with the indicated genotypes were dissected and weighed at 2 weeks (wild type [WT] or littermate control, n = 9; H1cH1dH1e−+−/−−−, n = 10), 4.5 weeks (wild type, n = 2; H1o−/−; H1cH1e−−/−−−, n = 4), and 11 weeks (wild type, n = 7; H1o−/−; H1cH1e−−/−−, n = 2). Weights are presented as averages ± standard deviations.