Effects of Desensitization on Different Kinds of in Vitro PPD-Induced Response of Lymph Node Lymphocytes from Tuberculin-Sensitive Guinea Pigs

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Abstract
Guinea pigs rendered hypersensitive to tuberculin 2-3 wk (early stage) or 10-14 wk (late stage) after sensitization with complete Freund''s adjuvant could be completely desensitized by a single or double injections of a sufficient amount of PPD (purified protein derivative). Lymph node cells from such desensitized animals 48-72 h after the challenge showed a considerable reduction of the ability to produce blastogenic factor and skin reactive factor upon PPD-stimulation, whereas the macrophage migration inhibitory factor activity remained unaffected. Lymph node cells from animals desensitized in the late stage after sensitization showed no substantial reduction in the degree of enhanced DNA synthesis upon PPD-stimulation, although the desensitization in the early stage resulted in a significant loss of this activity. Desensitizing challenge may not bring about a uniform and regular effect on every lymphocyte subpopulation relevant to different functions. There may be some exceptions to the compartmentalization concept of antigen-reactive lymphocytes.