Immunological changes during progressive stages of vitamin A deficiency in the rat.

The immune status of rats fed a vitamin A-deficient diet (-A) was studied before they reached the weight plateau (stage 1), during the first 5 d of the weight plateau (stage 2) and during late stages of vitamin A deficiency (stage 3). Compared to vitamin A-supplemented (+A) animals, there were no significant differences in the relative splenic weights during the early and later stages of deficiency, but the total yield of isolated splenocytes was lower in -A rats during stages 2 and 3. The weights of the cervical and mesenteric lymph nodes were higher during the later stages of deficiency. In the spleen, concanavalin A (Con A)-induced responses were significantly depressed in -A rats at all three stages of deficiency. In stages 2 and 3 splenic pokeweed mitogen (PWM) responses were lower in -A than in +A rats. There were no changes in lymph node responses in stage 1. The Con A and PWM-induced responses of cervical lymph nodes of -A animals were higher in stages 2 and 3. Mesenteric lymph node responses were also higher in -A rats in stage 3. The alterations in the transformation responses of -A rats could not be explained by changes in the relative proportions of T-cell subsets.