AJP - Regulatory, Integrative and Comparative Physiology, Vol 252, Issue 2 299-R305, Copyright © 1987 by American Physiological Society
Age-related changes in circannual rhythms of lymphocyte blastogenic responses in mice
M. A. Brock
Blastogenic responses to T- and B-lymphocyte mitogens were tested in
suspensions of splenocytes from 15- and 24- to 28-mo-old C57BL/6 mice and
compared with analogous responses in young animals. The mice were housed
under constant environmental conditions with alternating light-dark cycles
(LD 12:12). Single cell suspensions were cultured in vitro with mitogens,
and the induced incorporation of tritiated thymidine by dividing cells was
determined. Increases in periodicity of responses to concanavalin A and
phytohemagglutinin by T cells and to lipopolysaccharide by B cells and
lower mean levels of activation characterized rhythms in cells from
15-mo-old and senescent mice compared with young animals. Amplitudes of the
rhythms were unchanged at 15 mo, but by 24 mo of age rhythmic responses of
T but not B cells were damped. The separable effects of age on expression
of circannual rhythms by T and B lymphocytes suggest another mechanism for
imbalance in the immune system. Phases of depressed responses that are
extended for several months in populations of older mice could provide
increased opportunities for environmental assaults.
