IL-1 secretion and membrane IL-1 expression by neonatal spleen cells during soluble antigen presentation

Sex- and region-specific differences in microglia phenotype and characterization of the peripheral immune response following early-life infection in neonatal male and female rats

Early-life infection has been shown to have profound effects on the brain and behavior across the lifespan, a phenomenon termed "early-life programming". Indeed, many neuropsychiatric disorders begin or have their origins early in life and have been linked to early-life immune activation (e.g. autism, ADHD, and schizophrenia). Furthermore, many of these disorders show a robust sex bias, with males having a higher risk of developing early-onset neurodevelopmental disorders. The concept of early-life programming is now well established, however, it is still unclear how such effects are initiated and then maintained across time to produce such a phenomenon. To begin to address this question, we examined changes in microglia, the immune cells of the brain, and peripheral immune cells in the hours immediately following early-life infection in male and female rats. We found that males showed a significant decrease in BDNF expression and females showed a significant increase in IL-6 expression in the cerebellum following E.coli infection on postnatal day 4; however, for most cytokines examined in the brain and in the periphery we were unable to identify any sex differences in the immune response, at least at the time points examined. Instead, neonatal infection with E.coli increased the expression of a number of cytokines in the brain of both males and females similarly including TNF-α, IL-1β, and CD11b (a marker of microglia activation) in the hippocampus and, in the spleen, TNF-α and IL-1β. We also found that protein levels of GRO-KC, MIP-1a, MCP1, IP-10, TNF-α, and IL-10 were elevated 8-hours postinfection, but this response was resolved by 24-hours. Lastly, we found that males have more thin microglia than females on P5, however, neonatal infection had no effect on any of the microglia morphologies we examined. These data show that sex differences in the acute immune response to neonatal infection are likely gene, region, and even time dependent. Future research should consider these factors in order to develop a comprehensive understanding of the immune response in males and females as these changes are likely the initiating agents that lead to the long-term, and often sex-specific, effects of early-life infection.

Post natal ontogeny of immunological responsiveness in Merino sheep

Sheep in five age groups (two weeks, 10 weeks, 18 weeks, six months and four years old) were immunised systemically, twice, with ovalbumin or Brucella abortus (live or killed) and antibody responses in blood were measured. The animals were also infected with the nematode parasites Trichostrongylus colubriformis and Haemonchus contortus and faecal egg counts and serum antibody responses to larval antigens were measured. The experiments were designed so that, as far as possible, the effect of age per se could be dissociated from the combined effects of age and prior exposure to antigen. The effects of the age of sheep were more marked for antibody responses to Brucella abortus lipopolysaccharide than to ovalbumin. Older animals had much greater resistance to infection with internal parasites, as shown by the magnitude of the faecal egg count. In contrast to older lambs, neonatal lambs (infected with H contortus at two weeks old) had consistently declining concentrations of anti-H contortus antibody in their serum, mounted no detectable autogenous anti-H contortus antibody response in blood and appeared to develop no resistance to the parasite. Post natal ontogeny of immune responses was different for the various antigens/pathogens.

Interleukin-1 secretion by blood monocytes of septic premature infants

This study examined lipopolysaccharide (LPS) induced in vitro secretion of interleukin-1 (IL-1) by peripheral blood monocytes from pre-term infants with and without sepsis. Thirteen pre-term babies were tested; eight were completely healthy and five suffered from six episodes of sepsis. The latter group was tested both in the acute septic phase and in the convalescent period. IL-1 secretion by monocytes derived from septic pre-term infants was lower, but not significantly different from healthy pre-term infants (7.1 +/- 1.0 U/ml versus 8.1 +/- 0.9 U/ml, respectively). IL-1 secretion by monocytes of eight control full-term babies was in the same range (8.4 +/- 0.6 U/ml). In the convalescent period IL-1 secretion by monocytes from septic pre-term babies increased (9.0 +/- 0.3 U/ml) and was significantly higher than values measured during acute infection (p less than 0.05). Septic premature babies were also found to have higher absolute blood neutrophil concentration (p less than 0.001), but their body temperature did not increase along the infectious stage. The decreased secretion of IL-1 by monocytes from pre-term babies in the acute phase of infection compared to the convalescent period may have contributed to their inability to mount appropriate immunological as well as inflammatory responses. Sepsis promoting IL-1 production in vivo may have limited the monocytes' capacity for LPS stimulated IL-1 synthesis in vitro.

Effects of indomethacin and calcitonin on bone absorption in type II collagen-induced otosclerosis-like lesions in rats

In this study, we determined the effects of indomethacin and calcitonin on bone resorption in otosclerosis-like lesions in rats. Morphometric analysis showed that both indomethacin and calcitonin inhibited active otosclerosis-like lesions (bone resorption) and rats immunologically induced with type II collagen, and indomethacin had a much higher inhibitory effect than calcitonin. In in vitro studies we found that conditioned medium from splenic lymphocytes of rats immunized with type II collagen stimulated collagenase production by macrophages and fibroblasts. Collagenase is the major enzyme for degradation of the organic components of bone. Treatment of the immunized rats with indomethacin and calcitonin significantly reduced the stimulatory effect of the lymphocyte-conditioned medium on collagenase production. Indomethacin caused a greater reduction of the stimulatory effect of the lymphocytes on collagenase production than calcitonin. These findings are in agreement with results of the morphometric study. Results of the present study also suggest that cell-to-cell interaction plays an important role in collagenase production for degradation of organic components of bone resorption in otosclerotic lesions.

The immune response of offspring mice from mothers immunized during pregnancy with protein antigens

The immune system of offspring mice from mothers immunized with photo-oxidized timothy grass pollen antigen B (OX-AgB) or Trinitrophenyl-bovine gamma globulin (TNP-BGG) during their pregnancy was examined. Offspring mice immunized 6 or 8 weeks after delivery with the same antigen administered to their mothers have completely suppressed primary responses and greater than 80% suppressed secondary responses. The observed immunosuppression in offspring mice appears to persist until about 16 weeks after delivery, and is antigen-specific. Adoptive transfer studies show that spleen cells from adult OX-AgB primed mice injected i.v. into lethally X-irradiated (800 rads) syngeneic recipients and challenged with antigen produce significant levels of AgB-specific IgG antibody. Spleen cells (5 x 10(6] from offspring mice of mothers immunized with OX-AgB during their pregnancy were added to spleen cells from adult OX-AgB primed mice and injected i.v. into lethally X-irradiated syngeneic recipients and challenged with antigen. These recipients showed a significantly (greater than 85%) immunosuppressed secondary response. The observed immunosuppression appears to be mediated by CD4+ and CD8+ T cells suggesting a requirement for both T suppressor inducer and effector cell populations. The reported findings are discussed in relation to possible mechanisms to explain the immunosuppression obtained in the offspring of mothers immunized during pregnancy.

Antigen presentation by neonatal murine spleen cells

The ability of murine neonatal spleen cells to present soluble antigen to T-helper cells and to produce growth factors in response to subsequent cellular interactions was studied. The T-helper-cell line (D10-G4.1) (D10), which is specific for the soluble antigen conalbumin presented on H-2-matched (H-2k) antigen-presenting cells, was used as cooperating and indicator cells in these cellular interactions. The D10 cells are TH2 T-helper cells which secrete the autocrine growth factor IL-4 and can also respond to exogenous IL-2 (T. R. Mosmann and R. L. Coffmann, Immunol. Today 8, 223, 1987). D10 cells require exogenous IL-1 for their proliferation and secrete, in addition to IL-4, IL-1 inducer factor and GM-CSF. The ability of neonatal spleen cells to present antigen and to stimulate D10 cells to produce IL-4 and proliferate is low. During antigen presentation there is an augmentation of IL-1 and IL-2 production by the antigen-presenting spleen cell population. However, neonatal spleen cells do not respond to the same levels as do adult spleen cells. The addition of exogenous IL-1 cannot repair the antigen presentation by neonatal cells. Experiments in which the antigen processing and presentation steps were separated from those requiring growth factor induction and secretion demonstrate that neonatal spleen cells are impaired in their ability to perform adequate antigen processing and presentation. The neonatal spleen cells are as competent as adult cells to cooperate with T-helper cells and secrete growth factors, provided antigen processing and presentation is performed by fully competent adult spleen cells. Experiments in which neonatal and adult antigen-presenting spleen cell populations were mixed, and others in which plastic adherent and nonadherent cells were separated, could not detect any suppressor mechanisms responsible for the low antigen presentation of neonatal cells. Thus, neonatal spleen cells are impaired in the initial stages of antigen processing and presentation. This impairment which leads to low levels of growth factor production is the major determinant in the ineffectual stimulation of T-helper cells by neonatal spleen cells.