Immunodepression secondary to malnutrition: Assay by lymphocyte subset analysis using monoclonal antibodies and the cell sorter

It has been well documented that the hospitalized child frequently is malnourished, and the considerably greater morbidity and mortality of such children, in large part, is due to the associated secondary immunodepression. To assess the mechanism of such immunodepression in acute and chronically malnourished subjects, we chose an experimental murine model of malnutrition. Immune function was assayed by lymphocyte subset population and mixed lymphocyte culture (MLC) assessment, determining whether an alteration of the T helper (T_H) to T suppressor-cytotoxic (T_s-c) lymphocyte ratio is the mechanism that produces immunoincompetence in malnutrition. Ten-week-old A/J mice were rendered acutely or chronically malnourished by graded protein restriction using a 2.5% protein diet. These animals were studied before and after protein depletion with the fluorescent activated cell sorter (FACS) and the MLC. FACS cell populations were defined by the monoclonal antibodies to THY 1.2, LYT 1 (T_H), and LYT 2 (T_s-c) antigens. MLC reactivity was assessed with A/J v C 57 BL/6 mouse lymphocytes and expressed as a stimulation index (S.I.). Results are expressed in Table 1, and suggest that these malnourished animals were significantly immunodepressed as measured in the MLC reaction. However, the mechanism of this depression is not mediated by an inversion of the T_H/T_s-c ratio. These data contrast with those previously reported for the immunodepression of the burned or traumatized patient in which the T_H/T_s-c ratios are reversed; these data suggest that a different, as yet to be elucidated, mechanism exists for the immunodepression of malnutrition.