The correlation between immune dysfunction and raised CD4 : CD8 ratios seems to be confirmed by the studies conducted by Denholm et al. (3) and Malafaia et al. (14) in cattle, in which the consequences of subclinical phosphorus deficiency often included problems associated with reduced animal immunity and increased susceptibility to infectious diseases such as mastitis, metritis, brucellosis and other diseases affecting cow reproduction. The gene discussed is CD8A; the disease is brucellosis.