Rl. Davis et al., SPLENOCYTE SUBPOPULATIONS OF WEANLING COTTON RATS (SIGMODON HISPIDUS)ARE INFLUENCED BY MODERATE PROTEIN-INTAKE, Journal of mammalogy, 76(3), 1995, pp. 912-924
Populations of cotton rats (Sigmodon hispidus) frequently exhibit extr
eme fluctuations in abundance, which have been attributed to changes i
n food quality and its possible effect on survival of juveniles. Weanl
ing cotton rats fed low-protein diets experience altered immune-system
function. We evaluated the effects of moderate restriction of dietary
protein on splenocyte subpopulations of weanling cotton rats and dete
rmined the influences of onset of protein restriction at an earlier ag
e compared with previous studies. Weanling cotton rats (14 days old) w
ere fed three isocaloric diets containing 4, 8, or 16% protein for 24
days. Splenocyte subpopulations were assigned to one of eight categori
es by dual-staining with a panel of surface markers for T-cells (peanu
t agglutinin, PNA; soybean agglutinin, SEA, and Helix pomatia agglutin
in, HP) and B-cells (rabbit-anti-rat immunoglobulin-G, BS). Total numb
ers of all splenocyte subpopulations were lower in rats subjected to m
oderate (8%) or severe (4%) protein restriction; B-cells were more sen
sitive to protein restriction than were T-cells. Prevalence (percent o
f total splenocytes) of PNA(-)/BS+ splenocytes was reduced, whereas pr
evalence of PNA(+)/BS- and SBA(-)/HP+ splenocytes was elevated with de
creased protein intake. Multivariate statistical analysis of immune pa
rameters revealed peripheral blood lymphocytes and splenocyte subpopul
ations as well as hemolytic complement activity and mean corpuscular v
olume most accurately described the degree of protein restriction and
suggested a change in immunocompetence as a result of either moderate
or severe protein restriction.