Seasonal variation in cell mediated immunity of clinically normal dogs.

A whole blood lectin-induced lymphocyte stimulation test, using Con A and PHA, was used to assess the cell mediated immune status of 52 beagle dogs over a period of 16 months. The data indicated the presence of a seasonal variation in immune response with the peak estimated to be in July and an estimated trough in January. The relative amplitudes around the mean, for the two mitogens, were about 50%, so that the responses on lymphocyte division ranged from 50 to 150% of the mean during the course of the year. The possible implications of this finding for human health are discussed.