Impairment of suppressor-cell activity may be important in the pathogenesis and maintenance of insulindependent diabetes mellitus (IDDM). In 23 recent-onset IDDM patients, lymphocyte sensitivity in vitro to theophylline was tested both in basal conditions and after improvement of metabolic control. This pharmacologic agent is mainly effective on a lymphocytic subpopulation with phenotypic and functional suppressive features. Peripheral blood lymphocytes from IDDM patients showed a loss of theophylline sensitivity, identified as inhibition of both E-rosette formation and blastogenic response to polyclonal mitogens concanavalin A (ConA) and phytohemagglutinin (PHA). An inverse relationship was demonstrated between the theophylline-induced suppression of ConA blastogenic response and blood glucose and glycosylated hemoglobin levels (P < .01). Metabolic control seemed to be important even in relation to lymphocyte subpopulation distribution. In IDDM patients we found a significant (P < .05) reduction of OKT4+ lymphocytes that is correlated with blood glucose and glycosylated hemoglobin levels (P < .01). The improvement of metabolic control led to recovery of theophylline sensitivity. We suggest a deficiency in a suppressive system that could be involved in IDDM onset and the possible role of metabolic control in the impairment of some immunologic functions reported with this pathologic condition.

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