T cells with a quiescent phenotype (CD45RA+) are overabundant in the blood and involuted lymphoid tissues in wasting protein and energy deficiencies.

The objective of this investigation was to determine the influence of distinct forms of acute weight loss on the expression of the quiescence marker, CD45RA, by T cells in several lymphoid compartments including the blood. Male and female weanling mice, CBA/J and C57BL/6J strains, were allocated to the following groups: ad libitum intake of a complete purified diet; restricted intake of the complete diet; and ad libitum intake of an isocaloric low-protein diet. The restricted intake protocol produced weight loss through energy deficiency (marasmic-type malnutrition), whereas the low-protein diet caused wasting through inadequate protein nitrogen and induced a condition mimicking incipient kwashiorkor. In one experiment, weanling mice of both strains were maintained for 14 days according to each of these dietary protocols and, in a supplementary study, C57BL/6J weanlings consumed either the complete diet or the low-protein diet ad libitum for 21 days. Zero-time control groups (19-days old and 23-days old in C57BL/6J and CBA/J strains, respectively) were included in the first experiment to control for ontogeny-related change. Expression of CD45RA was assessed by two-colour flow cytometry in CD4+ and CD8+ T cells from the spleen, mesenteric lymph nodes and blood. Within 14 days, energy-restricted mice exhibited a high percentage of CD4+ T cells expressing CD45RA in all three lymphoid compartments in both mouse strains (an average of 50% CD45RA+ versus 9% in well-nourished controls), and a similar outcome was apparent in the CD8+ subset (93% CD45RA+ versus 63%). Mice fed the low-protein diet required up to 21 days to exhibit the same imbalance within the CD4+ T-cell subset (33% CD45RA+ versus 4% in well-nourished controls). A shift toward a quiescent phenotype occurs throughout the peripheral T-cell system in acute wasting disease. Consequently, the quiescence-activation phenotype of blood T cells reflects the same index in secondary lymphoid organs in such pathologies. Naive-type quiescence among T cells is implicated as a component of depressed adaptive immunocompetence in the advanced stages of diverse forms of acute weight loss.