Seasonal variation of induction of contact sensitivity and of lymph node T lymphocytes in guinea pigs.

Guinea pigs sensitized with dinotrophenyl thiocyanate in complete Freund's adjuvant from November to February developed markedly lower contact sensitivity than animals sensitized during the rest of the year. The percentage of T cell rosettes (lymphocytes forming spontaneous rosettes with normal rabbit red cells) was concomitantly reduced in the lymph nodes but not in thymus or bone marrow during the winter months.