Lymphocyte Proliferation In Rats Research Articles

Effect of dehydroepiandrosterone on mitogen-induced lymphocyte proliferation and cytokine production in young and old F344 rats

The steroid hormone intermediate, dehydroepiandrosterone (DHEA), has been proposed as a therapeutic agent for the treatment of immunosenescence in mouse model. In the present study, the in vitro effect of DHEA on mitogen-induced lymphocyte proliferation and cytokine production was evaluated in a rat model. Spleen lymphocytes were isolated from young (4–6 months) and old (24–26 months) F344 rats and were incubated with DHEA for 30 min. The induction of lymphocyte proliferation, interleukin-2 (IL-2), and interferon-gamma (IFN-γ) production by concanavalin A (Con A) was measured in a culture medium supplemented with either fetal calf serum (FCS) or with serum-free medium (Nutridoma-SR, N-SR). The induction of lymphocyte proliferation and IL-2 production by Con A decreased significantly with age, whereas induction of IFN-γ increased with age. Treatment of lymphocytes with DHEA did not significantly alter Con A-induced proliferation or the production of IL-2 or IFN-γ by spleen lymphocytes isolated from either young or old rats. These data indicate that in vitro DHEA treatment appears to have no immunomodulatory effect on the age-related changes in mitogen-induced proliferation or cytokine production in rat lymphocytes.

Acute infusions of cocaine result in time- and dose-dependent effects on lymphocyte responses and corticosterone secretion in rats

In the present study, we investigated the effect of intravenously (i.v.) administered cocaine on mitogen-induced lymphocyte proliferation and NK cytolytic activity in rats implanted with indwelling jugular cannula. To assess whether the effects of cocaine were accompanied by adrenal gland activation, plasma corticosterone concentrations were also determined. It was found that the i.v. infusion of cocaine resulted in both a time- and dose-dependent decrease in both blood and splenic Con-A-stimulated lymphocyte proliferative responses. Within 60 minutes, blood responses were maximally inhibited by more than 60% with 5 mg/kg cocaine. By 4 h, the suppression of blood lymphocyte responses was no longer significant. In contrast to these findings, there were no significant effects observed with splenic lymphocyte responses until 4 h after drug administration. At this time, cocaine at doses of 5 and 10 mg/kg inhibited splenic proliferative responses by 50 and 75%, respectively. These effects appeared to be selective, since no concurrent decreases in NK cell activity were observed with 5 mg/kg at either 2 or 4 h. Within 30 min, plasma corticosterone concentrations were maximally increased by 10-fold with 5 and 10 mg/kg doses of cocaine. At lower doses of cocaine (1 mg/kg), neither changes in lymphocyte proliferative responses, NK cytolytic activity nor plasma corticosterone levels were apparent. This study demonstrates that a single i.v. infusion of cocaine results in a selective dose- and time-dependent immunosuppression which is preceded by transient increases in circulating levels of corticosterone.

The effect of stressful behavioural exposure on endocrine and immune parameters in the rat

AbstractStress and depression are associated with a variety of alterations in the endocrine and immune systems. Leucocyte adhesiveness/aggregation (LAA) has recently been proposed as a simple indicator of stress in humans. The objective of the present study was to examine the serum concentration of corticosterone, neutrophil phagocytosis, lymphocyte proliferation, LAA and differential white blood cell (WBC) count in rats at different time intervals following an exposure to the behavioural despair and ‘open field’ tests. Thirty min following exposure to the behavioural despair test, the concentration of corticosterone was significantly elevated. An increase in the percentage of neutrophils and LAA, and a decrease in the percentage of lymphocytes and monocytes in the WBC count, were also found 30 min and 60 min after exposure to both the behavioural despair and ‘open field’ tests. A reduction in neutrophil phagocytosis was also observed 60 min after the exposure to these situations. The results show that there are endocrine and immune changes following exposure to these experimental situations. LAA appears to be a particularly useful indicator of acute stress in rats.

Effects of voluntary exercise on immune function in rats

We investigated effects of voluntary wheel running on specific antibody responses to Keyhole Limpet Hemocyanin (KLH) and on mitogen-stimulated lymphocyte proliferation in adult male rats. Each subject was placed in a running wheel for 12 h daily during the dark portion of the light cycle for a total of 8 weeks. For experimental animals the wheels rotated freely, enabling subjects to exercise at will, while for control animals the wheels were prevented from rotating. Subjects were immunized with KLH (25 μg) 5 weeks into the study, and blood samples were collected intermittently from the tail for 3 weeks and later assayed for anti-KLH antibody levels. At the end of the study, subjects were sacrificed and spleens were dissected and assayed for lymphocyte proliferative responses to the mitogen Concanavalin A. Exercised rats gained less weight and had higher splenic proliferative responses than control rats; however, there were no significant group differences in anti-KLH antibody levels.

Dietary Arginine Supplementation Does Not Enhance Lymphocyte Proliferation or Interleukin-2 Production in Young and Aged Rats

Recent studies indicate that supplemental arginine may enhance in vitro lymphocyte mitogenesis. To determine whether dietary arginine could reverse age-associated losses in immune functions, we fed purified amino acid diets to young (2-mo-old) and aged (24-mo-old) Fischer 344 rats. Rats receiving control (1.12% arginine) or supplemented (3% arginine) diets were pair fed to intakes of deficient (0% arginine) rats. Another group was fed the supplemented diet ad libitum. On d 15, responses of splenocytes to phytohemagglutinin (PHA), concanavalin A (Con A), and pokeweed mitogen (PWM) were lower (P less than 0.01), but interleukin-2 (IL-2) production was higher (P less than 0.05) in aged rats than in young rats. At mitogen doses producing maximal stimulation, supplemental arginine did not enhance PHA-, Con A- or PWM-stimulated lymphocyte proliferation; PWM responses at sub-maximal doses were higher in pair-fed supplemented rats than in control or ad libitum supplemented rats (P less than 0.05). Arginine supplements did not increase thymus weights or IL-2 production above controls. In another experiment, weanling rats received control and supplemented diets in amounts equal to the intake of deficient rats for an average of 37 d. Splenocytes were cultured with mitogens at various arginine levels. No diet effect was observed. Mitogenesis was maximal when media arginine approximated normal plasma levels. Our results suggest that supplemental arginine has little effect on lymphocyte proliferation or IL-2 production in healthy young and aged rats.

Effect of Dietary Iron Overload on Lipid Peroxidation, Prostaglandin Synthesis and Lymphocyte Proliferation in Young and Old Rats

The effect of dietary iron overload on lipid peroxidation (LP), prostaglandin (PG) synthesis and lymphocyte proliferation was examined in young and old F344 rats. Rats 4 and 19-22 mo old were fed AIN-76 diet for 11-12 wk supplemented with 2.5% carbonyl iron obtained from two sources (Type A and B). Animals supplemented with Type A iron showed reduced food intake and weight gain associated with marked increases in extrahepatic and hepatic iron concentration. Rats receiving Type B iron had food intakes and body weights similar to those of controls but exhibited small increases in tissue iron concentration. Old control rats compared to young had significantly higher conjugated dienes (CD) in hepatic microsomes. Feeding Type A iron diets induced a significantly higher level of CD in hepatic microsomes from old rats compared to young rats. Iron overloaded rats also showed highly correlated (r = 0.94) increases in the urinary excretion of thiobarbituric acid-reactive substances and PG metabolites indicating increased in vivo LP and PG synthesis. Mitogen-stimulated PGE2 synthesis in young rats was increased at 4 wk in association with enhanced T-cell proliferation stimulated by Concanavalin A. Lymphocyte proliferation was significantly lower in old than in young control or iron-treated rats. The lack of efficacy of Type B vs. Type A iron appears due to a larger particle size and lower bioavailability. In conclusion, iron overloading increases in vivo LP and PG metabolism. Furthermore, the mitogenic response to Concanavalin A in young rats is enhanced after 4 wk of iron overloading.

Identification of multiple associative and dissociative proliferative and uveitogenic T-cell sites in human interstitial retinoid-binding protein

Human interstitial retinoid-binding protein (HIRBP) is a 136 kDa retinal protein capable of inducing experimental autoimmune uveoretinitis (EAU) and experimental autoimmune pinealitis (EAP) in Lewis (LEW) rats. In order to identify the T-cell recognition sites of HIRBP responsible for uveitogenic and proliferative responses, 125 overlapping peptides corresponding to its entire 1262 amino acid sequence were synthesized. Individual peptides were tested for their ability to induce EAU in LEW rats and to stimulate lymphocyte proliferation in rats immunized with the native molecule. Our previous results showed the presence of nine uveitogenic peptides in HIRBP with a minimum requirement of eight amino acids needed to induce EAU in LEW rats. Our present studies show nine proliferative peptides, four of which are also responsible for uveitogenicity. Another four peptides known to actively induce EAU were unable to elicit proliferative responses. However, these peptides overlapped or were adjacent to peptides that elicited good proliferative responses. A single, highly proliferative peptide was located on the amino terminus of HIRBP. In addition, EAU was adoptively transferred with lymph node cells (LNC) of LEW rats previously immunized with two synthetic peptides known to be uveitogenic. Our study indicates that human IRBP is a complex molecule containing multiple and spatially distinct T-cell epitopes responsible for its uveitogenicity, adoptive transfer of EAU and proliferative responses.

The effect of zinc status on the immune function of diabetic rats.

To evaluate the role of zinc status in immune system dysfunction in diabetic animals, the interleukin-2 production and the lymphocyte mitogenic response to phytohaemagglutinin, concanavalin A and lipopolysaccharide were measured in streptozotocin-induced diabetic rats, diabetic rats treated with insulin and their non-diabetic controls maintained on low zinc, normal zinc and high zinc diets for 3 weeks. Unstimulated lymphocyte proliferation was significantly lower in diabetic rats compared to nondiabetic control rats maintained on normal zinc diet (1505 +/- 318 vs 3447 +/- 497 cpm) (p less than 0.005) or low zinc diet (546 +/- 191 vs 4011 +/- 628 cpm) (p less than 0.005). High zinc diet attenuated the difference between the diabetic rats (2404 +/- 833 cpm) and control rats (3929 +/- 713 cpm). Insulinised diabetic rats were similar to control rats. Phytohaemagglutinin-stimulated lymphocyte proliferation was not significantly altered with dietary zinc changes, but diabetic rats on low zinc diet had significantly lower (p less than 0.025) values compared to control rats on the same diet (41470 +/- 7874 vs 72308 +/- 8895 cpm). Insulinisation did not normalise phytohemaegglutinin-stimulated lymphocyte proliferation (40711 +/- 3666 cpm). Similarly, cells from diabetic rats on low zinc diet, unlike their controls, failed to respond to concanavalin A stimulation. Compared to control rats the diabetic rats on either low or normal zinc diets had lower lipopolysaccharide-stimulated lymphocyte proliferation. High zinc diet or insulinisation normalised mitogenic response of lymphocytes to lipopolysaccharide. Unlike the diabetic rats alterations in dietary zinc intake did not significantly affect the lymphocyte proliferation in control rats.(ABSTRACT TRUNCATED AT 250 WORDS)