Salivary concentrations of IL-8 and IL-1ra after HIIT and MICT in young, healthy adults: A randomized exercise study.

The purpose of this study was to determine whether six weeks of high intensity interval training (HIIT) would lead to greater changes in resting concentrations of salivary IL-8 and IL-1ra than moderate intensity continuous training (MICT) in young, healthy adults, and to determine whether changes in IL-8 and IL-1ra after six weeks of either HIIT or MICT were associated with changes in maximal exercise capacity (VO2max). Participants were randomly assigned to 6 weeks of HIIT (n = 12) or MICT (n = 11), matched for workload. Saliva samples were collected at the beginning (T1) and end (T2) of the intervention, and analyzed for IL-8 and IL-1ra. Participants in both groups had significant improvements in VO2max; there were no group differences in improvements. A greater reduction in IL-8 was observed in the MICT group when compared to the HIIT group (HIIT median: -9.5; MICT median: -82.3 pg/µg of protein; U = 11.5, p < 0.001). When combining the HIIT and MICT group, there were significant reductions in IL-8 from T1 to T2. There was no correlation between changes in IL-8 (r < 0.00) or IL-1ra (r = -0.013) with changes in VO2max. In conclusion, 6 weeks of exercise training leads to a reduction in IL-8; MICT may lead to greater reductions when compared to HIIT. Future research examining longer intervention periods is needed to further elucidate the effects of HIIT and MICT on different pro and anti-inflammatory cytokines.

Salivary IL-8 and IL-1RA changes induced by exercise in cold-dry and normal conditions.

The purpose of this study was to compare the effects of exercise in cold-dry (CC, -20 °C, RH 40%) and normal conditions (NC, 20 °C, RH 60%) on salivary levels of pro-inflammatory and regulatory cytokines (IL-1RA, IL-8, and IL-5) and the airway response (FEV1 and FVC) in young healthy males. Participants (n = 11, age: 23.6 ± 3.1 years) completed an incremental to maximal exercise test and two exercise sessions in an environmental chamber in random order. Saliva samples were collected, and spirometry was performed prior to the maximal exercise test as well as pre and post-exercise for the CC and NC sessions. IL-8 levels increased from pre to post-exercise during NC but not during CC; the opposite trend was observed for IL-1RA. These data may provide insight into pathways associated with the development of airway hyperresponsiveness in healthy athletes.

Characterization of casein-derived peptide bioactivity: Differential effects on angiotensin-converting enzyme inhibition and cytokine and nitric oxide production.

Lactic acid bacteria (LAB) are used as starter cultures in the production of fermented dairy products and have the potential to confer bioactivity relevant to cardiovascular health, as they possess extensive proteolytic systems that liberate small bioactive peptides from larger milk proteins. Certain casein-derived peptides released by various LAB strains during fermentation have been shown to reduce hypertension and to modulate the immune system. We investigated the growth and peptide production of 2 LAB strains, Lactobacillus helveticus R0389 and Lactocaseibacillus rhamnosus R0011, their immunomodulatory activities, as well as their abilities to inhibit the angiotensin-converting enzyme (ACE). Peptide fractions collected from the cell-free supernatant of both medium-grown and milk fermentation cultures were assessed for ACE-inhibitory activity and their effects on the production of proinflammatory and regulatory cytokines by human THP-1 monocytes. Cultures were grown in medium, with or without supplementation with 0.1% casein, or in 3.25% milk fermented with each LAB strain. Casein supplementation increased the growth rate of both LAB strains, and significantly increased ACE-inhibitory activity of peptide fractions collected from both L. helveticus R0389 and L. rhamnosus R0011 cultures grown for 12 h. Fermentation peptide fractions of L. rhamnosus R0011 showed comparable ACE-inhibitory activity to known ACE inhibiting peptides Val-Pro-Pro and Ile-Pro-Pro (up to 79% inhibition) with a significant difference between culture peptide fractions and acidified and nonacidified control fractions collected after 6 d of fermentation. Many milk and casein-derived peptides reported in previous studies have been identified as part of a larger bioactive fraction. We synthesized a group of these peptides to individually assess both ACE-inhibitory and immunomodulatory activity. The known ACE inhibitors Val-Pro-Pro and Ile-Pro-Pro showed similar ACE inhibition to previously published results, while also inducing the production of the regulatory cytokine IL-10 by monocytes in the presence and absence of a proinflammatory stimulant. These synthesized peptides could also induce the production of nitric oxide (NO), a potent vasodilator, in human endothelial cell cultures. Investigating the relationships among these bioactive properties could improve the use of probiotic organisms and their secreted products in the food industry.

Temporal change in the gut community of rats fed high amylose cornstarch is driven by endogenous urea rather than strictly on carbohydrate availability.

AIM: To examine change in the gut community of rats fed high amylose maize starch (HAMS). METHODS AND RESULTS: Rats were fed AIN93G diets containing HAMS (5% resistant starch type 2) or alphacell (control). HAMS increased faecal short-chain fatty acid output, faecal propionate and total bacteria output but reduced gut pH and blood urea concentrations compared with rats ingesting the control diet. Feeding HAMS resulted in a gut community dominated by four phylotypes homologous with Ruminococcus bromii, Bacteroides uniformis and with yet to be cultivated organisms aligning into the Family Porphyromonadaceae. Enrichment of phylotypes aligning within the Bacteroidetes occurred primarily in the caecum, whereas those homologous with R. bromii were found primarily in the faeces. HAMS altered community structure such that the phylum Bacteroidetes represented the dominant gut lineage and progressively reduced faecal community phylotype richness over the duration of feeding. CONCLUSIONS: Feeding HAMS resulted in a caecal and faecal community dominated by organisms that require ammonia as a primary nitrogen source. Gut ammonia derived from endogenous urea represents an important factor contributing to caecal community composition in addition to the ability to utilize HAMS. Increases in faecal propionate, rather than butyrate as is often observed following resistant starch feeding, reflected a gut community dominated by the Bacteroidetes. SIGNIFICANCE: Diet-mediated change is often viewed strictly in terms of available carbohydrate. Here, we have shown that ammonia derived from endogenous urea is an important factor contributing to gut community composition and structure in rats fed this substrate.

Effect of feeding fresh forage and marine algae on the fatty acid composition and oxidation of milk and butter.

This study evaluated the effects of feeding fresh forage either as pasture plus a concentrate (PAS) or as a silage-based total mixed ration (TMR), combined with either a ruminally inert lipid supplement high in saturated fatty acids (-) or a ruminally protected microalgae containing 22 g of docosahexaenoic acid (DHA)/100 g of fatty acids (+) on the fatty acid (FA) composition and oxidation of milk and butter. For the 8 mid-lactation Holstein cows in this study, milk yield was not significantly affected by treatment, averaging 32.3 ± 1.28 kg/d. Milk fat content was higher for PAS⁻, averaging 5.05 compared with 4.10 ± 0.17% for the mean of other treatments, and was significantly depressed with microalgae supplementation (3.97 vs. 4.69 ± 0.17%). The saturated fatty acid level in the milk of cows fed TMR⁻ was significantly higher than that of the other treatments (66.9 vs. 61.2 g/100 g of FA). The level of monounsaturated FA was lowered by feeding TMR⁻ (27.4 vs. 32.0 g/100 g of FA), whereas levels of polyunsaturated FA were elevated by feeding PAS+ compared with the mean of the other treatments (6.54 vs. 5.07 g/100 g of FA). Feeding the rumen-protected microalgae increased the DHA content of milk more than 4-fold (0.06 to 0.26 g/100g of FA) with the PAS treatment. The conjugated linoleic acid content of milk was highest for PAS+ compared with the other treatments (4.18 vs. 3.41 g/100g of FA). In general, the fatty acid composition of butter followed that of milk. Overall, feeding the TMR supplemented with the rumen-protected microalgae increased the levels of volatile products of oxidation in milk and butter. No effect of forage type or microalgae supplementation was observed on the oxidative stability or antioxidant capacity of milk, although the oxidative stability of butter exposed to UV was reduced with microalgae supplementation, particularly with TMR, as assessed by using the ferric reducing ability of plasma assay.

Immunomodulatory properties of fermented soy and dairy milks prepared with lactic acid bacteria.

Fermented soy and dairy milk preparations provide a means for delivering lactic acid bacteria and their fermentation products into the diet. Our aims were to test immunomodulatory bioactivity of fermented soy beverage (SB) and dairy milk blend (MB) preparations on human intestinal epithelial cells (IEC) and to determine the impact of freezing medium on culture survival prior to bioactivity analyses. Fermented SB and MB were prepared using pure or mixed cultures of Streptococcus thermophilus ST5, Bifidobacterium longum R0175, and Lactobacillus helveticus R0052. Immunomodulatory bioactivity was assessed by testing selected SB and MB ferments on tumor necrosis factor alpha (TNFalpha)-treated IEC and measuring effects on Interleukin-8 (IL-8) production. Impact of timing of ferment administration relative to this pro-inflammatory challenge was investigated. The most pronounced reductions in IEC IL-8 production were observed when IEC were treated with either SB or MB ferment preparations prior to TNFalpha challenge. These results indicate that freezing-stable MB and SB ferments prepared with selected strains can modulate IEC IL-8 production in vitro, and suggest that yogurt-like fermented soy formulations could provide a functional food alternative to milk-based fermented products.

Activation of rat alveolar macrophage-derived latent transforming growth factor beta-1 by plasmin requires interaction with thrombospondin-1 and its cell surface receptor, CD36.

Transforming growth factor-beta-1 (TGF-beta1) is secreted by cells in a latent form (L-TGF-beta1) noncovalently bound to a latency-associated peptide. Activated alveolar macrophages obtained from rat lungs after bleomycin-induced pulmonary injury released increased amounts of active TGF-beta1 as well as plasmin, a protease, and thrombospondin-1 (TSP-1), a trimeric glycoprotein. Previously we had demonstrated that plasmin was critical to the activation of L-TGF- beta1. In the present study we demonstrated that TSP-1 is also important for the activation of L-TGF- beta1 because the activation can be inhibited by anti-TSP-1 monoclonal antibody. Proteins obtained from alveolar macrophage cell lysates immunoprecipitated with antibodies specific for TSP-1 were identified on immunoblots as LAP and TGF-beta1, indicating that TSP-1/L-TGF-beta1 complexes are present on alveolar macrophages. However, in the presence of plasmin both latency-associated peptide and TGF-beta1 were decreased in the same cell lysates, indicating that L-TGF-beta1 associated with TSP-1 is released by plasmin. Using immunofluorescence and antibodies to TGF-beta1 and CD36, a receptor for TSP-1, there was colocalization of TGF-beta1 with CD36. Because TSP-1 but not TGF-beta1 is a natural ligand for CD36, these findings suggest that the L-TGF-beta1 in a complex with TSP-1 localizes to the macrophage cell surface when TSP-1 interacts with its receptor, CD36. Furthermore, the association of TSP-1/L-TGF-beta1 complex with CD36 is necessary to the activation of L-TGF-beta1 because antibodies to CD36 prevent the colocalization of TGF-beta1 with CD36 as observed by immunofluorescence and inhibit activation of the L-TGF-beta1 by explanted alveolar macrophages. These findings suggest that activation of L-TGF-beta1 by plasmin occurs at the cell surface of activated alveolar macrophages and requires a TSP-1/CD36 interaction.

Pavlovian conditioning of LPS-induced responses: effects on corticosterone, splenic NE, and IL-2 production.

The present study used a taste aversion paradigm to condition lipopolysaccharide (LPS)-induced suppression of splenic lymphocyte interleukin-2 (IL-2) production, with concurrent measurement of corticosterone production and splenic norepinephrine (NE) content). In training, two groups of rats received saccharin and IP LPS in a paired (P) manner and a third group in a specifically unpaired (U) manner. In the test, the unpaired group (group U) and one of the paired (group P) groups were re-exposed (R) to the cue and the other not (NR). An additional group controlled for the effects of cues (conditional stimulus) and fluid deprivation (negative control; NC). A robust taste aversion in the P-R group was accompanied by suppression of IL-2 production, reduced splenic NE content, and elevated corticosterone production, relative to combined controls (i.e., groups U-R, P-NR, and NC). The conditioned modulation of IL-2 secretion, along with the concomitant alteration of adrenocortical and sympathetic mediators, supports the involvement of bidirectional central nervous-immune system pathways in this paradigm.

Role of norepinephrine in suppressed IgG production in epilepsy-prone mice.

The responses of two substrains of Balb/c mice (Epilepsy Prone and Epilepsy Resistant) to immunization with sheep red blood cells (SRBC) were examined to determine whether chronic neurochemical differences between the two strains could influence B cell function. Anti-SRBC IgG production in the Epilepsy Prone (EP) strain was reduced relative to the Epilepsy Resistant (ER) strain, while anti-SRBC IgM production was unaffected. No differences were found in in vitro antibody (Ab) production or T lymphocyte function between the EP and ER strains, suggesting that in vivo conditions rather than an intrinsic cellular defect are responsible for reduced IgG production by EP mice. Basal splenic norepinephrine (NE) levels were significantly higher in EP mice than those in ER mice, and remained significantly higher following immunization. ER mice treated with the beta 2 adrenergic agonist terbutaline on days 4, 5 and 6 after immunization produced significantly lower numbers of IgG PFC than did saline treated controls. Addition of NE during later stages of in vitro immunization suppressed both anti-SRBC IgM and IgG production by splenic lymphocytes from Balb/c mice, and NE was found to decrease IFN gamma production. These observations suggest that dysregulation of splenic NE can have an impact on the immune response.

Suppressed T cell and macrophage function in the "reeler" (rl/rl) mutant, a murine strain with elevated cerebellar norepinephrine concentration.

The effects of neurochemical alterations in specific brain regions on the immune system were examined in reeler (rl/rl) mice, a neurologic mutant strain having an abnormally high concentration of cerebellar norepinephrine (NE). Following immunization with sheep red blood cells, lower numbers of IgM-producing B cells were found in rl/rl mice than in B6C3Fea/a controls. Interleukin-1 (IL-1) production by splenic macrophages from rl/rl mice was reduced compared to B6C3F3a/a controls, as was the proliferative response of splenic T lymphocytes from rl/rl mice activated with an anti-CD3 monoclonal antibody. Levels of IL-4, interferon-gamma and IL-2 produced by splenic T lymphocytes from rl/rl mice were also lower than those of B6C3Fea/a controls. Rl/rl mice do not have an intrinsic defect in the ability to produce IgM, as lipopolysaccharide activated splenic lymphocytes from rl/rl mice produced levels of IgM similar to those of controls. This suggests that defective function in the T lymphocyte and/or macrophage population rather than in the B cell population may underlie the defect in IgM production. No significant alterations were observed in basal splenic levels of NE or neuropeptides in rl/rl mice relative to controls. The reeler mouse model shows that alterations in immune function are present in a strain with inherited alterations in cerebellar noradrenergic innervation and NE concentration.

The effects of kainic acid-induced lesions in the lateral septal area on cell-mediated immune function.

The lateral septal area (LSA) is a primary control region for psychoneuroendocrine functions, and we have previously reported that kainic acid (KA) lesions in the LSA and the hippocampus have inhibitory and facilitatory effects, respectively, on the humoral immune response of female rats. Thus, these limbic structures may selectively participate in directing neuroimmune regulation. In order to assess the fundamental role of the LSA in neuroimmune regulation, we have evaluated the effects of neurotoxic septal lesions on various cell-mediated immune measures. Animals received stereotaxically guided bilateral infusions of KA (2.0 micrograms/microliter) or physiological saline (SHAM) into the LSA. Following a 2-week recovery period, animals were sacrificed and the spleen cells analyzed for natural killer (NK) cell activity and T-cell responsiveness to mitogen (ConA) or to anti T-cell receptor mAb (R73). A separate group of LSA-lesioned animals were immunized with sheep red blood cells 4 days prior to harvesting the spleen for plaque forming cell (PFC) number determination and measurement of TNF-alpha secretion from splenic macrophages. The results indicate that rats with KA lesions in the LSA have significantly higher NK cell activity, significantly lower numbers of splenic PFCs, and significantly reduced TNF-alpha secretion from splenic macrophages, relative to controls. There was a statistical tendency (p < .1) for reduced T-cell lymphoproliferative responses to ConA stimulation in LSA-lesioned animals, relative to SHAMs. However, the T-cell lymphoproliferative response to specific activation via the T-cell receptor was not significantly different between lesioned and control groups. These results further demonstrate the importance of KA-sensitive LSA neurons in neuroimmunoregulation. Moreover, selective alterations of different components of the immune system are observed in LSA-lesioned animals, suggesting that the LSA is involved in the complex and differential regulation of immunity.

Interleukin-2-induced enhancement of an antigen-specific IgM plaque-forming cell response is mediated by the sympathetic nervous system.

Interleukin (IL)-2, a lymphokine produced by activated T-cells, stimulates T-cell proliferation and differentiation and potentiates B-cell production of antigen-specific immunoglobulins. IL-2 also increases hypothalamic norepinephrine turnover without affecting plasma corticosterone levels, which suggests that it selectively impacts on central sites that mediate sympathetic outflow to lymphoid organs. Because sympathetic stimulation during the early phases of an immunoglobulin (Ig)M plaque-forming cell (PFC) response to sheep red blood cells results in an increase in the subsequent number of antibody-forming cells, we assessed whether the enhancing effects of IL-2 on the PFC response are mediated by the sympathetic nervous system. The peak splenic IgM PFC response was increased in male Sprague-Dawley rats and BALB/c mice administered recombinant human IL-2 (50, 100 or 200 ng i.p.) in close temporal congruity with sheep red blood cell administration (i.e., 1 day before or immediately before immunization), compared with vehicle-treated controls. IL-2 administered at a later interval after immunization (i.e., 2 days) did not increase the number of antibody-forming cells. Intact sympathetic innervation of the spleen was required for the IL-2-induced immunoenhancement to occur because cutting the splenic nerve 10 days prior to IL-2 administration blocked the lymphokine's potentiation of the IgM PFC response. The immunostimulatory effects of IL-2 were also blocked in mice administered the beta adrenergic antagonist propranolol (5 mg/kg) immediately and 1 day after IL-2 administration. The alpha adrenergic antagonist phentolamine (5 mg/kg) had no effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Cytokine-specific central monoamine alterations induced by interleukin-1, -2 and -6.

Cytokine-specific alterations of monoamine activity were evident in the hypothalamus, hippocampus and prefrontal cortex 2 h following peripheral administration of recombinant interleukin (IL)-1 beta, IL-2 and IL-6 (200 ng, i.p.) in male, BALB/c mice. IL-1 induced the broadest range of neurochemical changes, affecting central norepinephrine (NE), serotonin (5-HT) and dopamine (DA) activity. In particular, IL-1 enhanced NE turnover in the hypothalamus and hippocampus, 5-HT turnover in the hippocampus and prefrontal cortex (owing to increased utilization and reduced content of the transmitters in these brain regions), and enhanced DA utilization in the prefrontal cortex. IL-6 increased 5-HT and DA activity in the hippocampus and prefrontal cortex in a manner similar to IL-1, but failed to affect central NE activity. Moreover, IL-2 increased hypothalamic NE turnover (reflecting a profound increase in NE utilization) and enhanced DA turnover in the prefrontal cortex, but did not influence central 5-HT activity. Hence, these cytokines differentially altered neurochemical activity in brain regions that mediate neuroimmune interactions and that are influenced by physical and psychological stressors. In addition to the neurochemical changes, plasma corticosterone concentrations were profoundly enhanced in IL-1-treated animals, but not significantly altered by IL-2 or IL-6 treatment. The IL-1-induced corticosterone elevations did not significantly correlate with alterations of hypothalamic NE activity.

Determination of amino acids and monoamine neurotransmitters in caudate nucleus of seizure-resistant and seizure-prone BALB/c mice.

Amino acid and monoamine concentrations were examined in tissue extracts of caudate nucleus of genetic substrains of BALB/c mice susceptible or resistant to audiogenic seizures. Amino acids [aspartate, glutamate, glycine, taurine, serine, gamma-aminobutyric acid (GABA)], monoamines, and related metabolites were separated by isocratic reverse-phase chromatography and detected by a coulometric electrode array system. In situ activity of tyrosine hydroxylase and tryptophan hydroxylase were determined by measuring the accumulation of L-DOPA and 5-hydroxytryptophan after administration of the decarboxylase inhibitor NSD-1015. Highly significant decreases in concentrations of both excitatory (glutamate and aspartate) and inhibitory amino acids (GABA and taurine) were observed in extracts of caudate nucleus of seizure-prone mice. Substantial decreases in concentrations of dopamine (DA) and its metabolites, 3,4-dihydroxyphenylacetic acid and homovanillic acid, were also noted. Decreased accumulation of L-DOPA after NSD-1015 administration provided evidence for decreased tyrosine hydroxylase activity and decreased DA synthesis in striatum of seizure-prone mice compared with seizure-resistant mice. Decreased concentrations of the DA metabolite 3-methoxytyramine (after NSD-1015 administration) suggested that DA release was also compromised in seizure-prone mice. No significant difference in 5-hydroxytryptophan accumulation in striatum of seizure-prone and seizure-resistant mice suggested that tryptophan hydroxylase activity and serotonin synthesis were not affected. The data suggest that seizure-prone BALB/c mice have a deficiency in intracellular content of both excitatory and inhibitory amino acids. The data also raise the issue of whether GABAergic interactions with the nigrostriatal DA system are important in the regulation of audiogenic seizure susceptibility.

Regional accumulation of Pgp-1+ memory cells in senescent mucosal immune system.

The proportion of memory cells expressing the Pgp-1 surface marker, and subsets of T cells expressing L3T4 (CD4+ helper cells), Lyt-2 (CD8+ suppressor/cytotoxic cells), LFA-1 (lymphocyte function-associated antigen-1), and interleukin-2 receptors (IL-2R) on the cell surface in the spleen, regional lymph nodes (PLN), mesenteric LN (MLN), bronchial or mediastinal LN (BLN), Peyer's patches (PP), thymus, and bone marrow (BM) was studied in C57BL/6J mice of varying ages. Monoclonal antibodies (Mabs) IM7.8.1, FD4, GK1.5, 3.155, and FD441.8 were used to measure Pgp-1, IL-2R, L3T4 Lyt-2, and LFA-1 expressions, respectively. Optimal dose and kinetic studies were determined. The percentages of positive cells were determined by monoclonal antibody staining and flow cytometry or immunofluorescence microscopy. Using flow cytometric analysis, we found significant age-associated increases in the percentages of Pgp-1+ cells in the MLN as compared with a slight, but not significant, increase in the spleen. There were significant age-related increases in the percentages of Lyt-2+ cells in the spleen with no change in the MLN. The percentages of cells with the other phenotypic markers, L3T4, LFA-1, and IL-2R did not change with age in the spleen or MLN. Using immunofluorescence microscopy, the percentages of Thy-1.2+, Lyt-1+, and Lyt-2+ cells in different anatomical immune tissues did not change with age, except in the BLN and PP where there were significant age-related declines of the percentages of Thy-1.2+ and Lyt-2+ cells in the BLN, and of Lyt-1+ cells in the PP. These results indicate elevated levels of Pgp-1+ memory senescent cells in the MLN and these age-related shifts or changes in T lymphocyte subsets with age could contribute to the conserved immune responsiveness of senescent mucosal T lymphocytes.

Proliferative capacity of senescent lymphocytes. II. Monoclonal antibody stimulation of mucosal and systemic lymphocytes via T cell activation molecules, CD3 epsilon, T cell receptor V beta 8 chain, and phosphatidylinositol-linked anchored receptors THY-1 and LY-6A.2/TAP.

The proliferative capacity of senescent mucosal and systemic lymphocytes was studied in response to monoclonal antibody (Mab) stimulation of T cell activation molecules, CD3 epsilon, V beta 8a chain of the T cell receptor (TcR-V beta 8), Thy-1, and Ly-6A.2/TAP. The percentage of positive cells, fluorescence intensities, and proliferative responses of lymphocytes from the spleen and mesenteric lymph nodes (mln) of individual C57BL/6J male mice were compared at 2, 4, 12, 20, and 30 months of age. Mabs F23.1, 145-C11, Jij.10, and D7 were used to measure TCR-V beta 8a, CD3 epsilon, Thy-1, and Ly6A.2/TAP expressions, respectively. Optimal dose and kinetic studies were determined. There were no significant age-related changes in the percentage of splenic cells expressing CD3 epsilon, TCR-V beta 8a, Thy-1, and Ly6A.2, as well as their fluorescence intensities on the cell surface as measured flow cytometry. For mln cells, the percentage of cells expressing TCR-V beta 8a, Thy-1, and Ly6A.2 did not significantly change with age. A significant age-related increase was found in the percentage of mln cells expressing CD3 epsilon. The fluorescence intensities of CD3 epsilon, TCR-V beta 8a, and Ly6A.2 expression on the cell surface of mln cells significantly increased with age. Mabs anti-TcR-V beta 8a and anti-CD3 epsilon stimulation of splenic lymphocytes in culture for 3 days revealed a significant decline in proliferative responses after 12 months of age. When splenic cells were stimulated with Mab anti-CD3 epsilon in combination with optimal doses of phorbol myristate acetate (PMA) in culture for 3 days, there was a two-fold elevation in the proliferative response with a significant decline occurring after 20 months of age. Mab anti-TcR-V beta 8a and Mab anti-CD3 epsilon plus PMA stimulation of mln lymphocytes consistently revealed a significant decline in proliferative responses only after 20 months of age. Both splenic and mln cells showed a significant decline in proliferative responses to Mab anti-Thy-1 stimulation after 12 months of age. There was no age-related change in the proliferation of splenic and mln cells to Mab anti-Ly6A.2 activation. These results indicate that the onset and rate of age-related decline in the proliferative capacity of lymphocytes after stimulation with Mabs anti-CD3 epsilon and anti-TcR-V beta 8 chain changes much later and slower in the mln than those of the spleen.(ABSTRACT TRUNCATED AT 400 WORDS)