Cellular and humoral immunity in a wild mammal: Variation with age & sex and association with overwinter survival

Immune defenses are expected to be crucial for survival under the considerable parasite pressures experienced by wild animals. However, our understanding of the association between immunity and fitness in nature remains limited due to both the complexity of the vertebrate immune system and the often‐limited availability of immune reagents in nonmodel organisms. Here, we use methods and reagents developed by veterinary researchers for domestic ungulates on blood samples collected from a wild Soay sheep population, to evaluate an unusually broad panel of immune parameters. Our evaluation included different innate and acquired immune cell types as well as nematode parasite‐specific antibodies of different isotypes. We test how these markers correlate with one another, how they vary with age‐group and sex, and, crucially, whether they predict overwinter survival either within or among demographic groups. We found anticipated patterns of variation in markers with age, associated with immune development, and once these age trends were accounted for, correlations among our 11 immune markers were generally weak. We found that females had higher proportions of naïve T cells and gamma–delta T cells than males, independent of age, while our other markers did not differ between sexes. Only one of our 11 markers predicted overwinter survival: sheep with higher plasma levels of anti‐nematode IgG antibodies were significantly more likely to survive the subsequent high mortality winter, independent of age, sex, or weight. This supports a previous finding from this study system using a different set of samples and shows that circulating antibody levels against ecologically relevant parasites in natural systems represent an important parameter of immune function and may be under strong natural selection. Our data provide rare insights into patterns of variation among age‐ and sex groups in different T‐cell subsets and antibody levels in the wild, and suggest that certain types of immune response—notably those likely to be repeatable within individuals and linked to resistance to ecologically relevant parasites—may be most informative for research into the links between immunity and fitness under natural conditions.     

Comparative studies on monotypic IgMlambda and IgGkappa from an individual patient. I. Evidence for shared VH idiotypic determinants.

A comparative idiotypic antigenic analysis of an IgMlambda and an IgGkappa paraprotein obtained from sera of an individual patient, Br, revealed the presence of very similar idiotypic determinants associated with the VH regions of the Br mu- and gamma-chains. In addition, the IgGkappa protein expressed light (L) chain-associated idiotypic determinants which were not evident on the IgMlambda protein or its isolated L chains. Extensive tests of specificity revealed that the shared VH idiotypic determinants were not present in large weight amounts of heterologous nonspecific IgM and IgG, nor on Ig molecules contained in a large number of normal and myeloma sera.     

CELL POPULATION CHANGES IN THE INTESTINAL MUCOSA OF PROTEIN-DEPLETED OR STARVED RATS : II. Changes in Cellular Migration Rates

The effect of protein-free and starvation diets on the migration of cells from the crypts onto and up the villi of the rat ileum was studied. Rats starved for 3, 7, or 10 days or fed a protein-free diet (PFD) for 3, 7, or 11 wk were injected with thymidine-³H and sacrificed at timed intervals. The time required for the labeled cells to first appear on the villi of experimental animals was longer than in the controls. This was the result of an elongated cycle in the protein-depleted animals and a lengthening of the maturation period in both the starved and protein-depleted animals. Determination of the distance which labeled cells had migrated up the villi in control and experimental animals, after thymidine-³H injection, indicated that cells in animals starved for 7 days migrated more rapidly than those in the fed controls, while those of 10-day starved animals moved more slowly. The cells of animals fed PFD for 3 wk migrated up the villi more rapidly, those of animals depleted for 7 wk migrated at the same time rate, and those of 11-wk PFD animals migrated more slowly than the fed controls. There is apparently no correlation between the cell cycle time in the crypt cells and the rate of migration of cells up the villus.     

Mutation of a Heterothallic Strain to Homothallism

Upon mutagenesis, a heterothallic αα diploid strain mutated to homothallism. The gene confering homothallism is nuclear, recessive, and unlinked to mating type. This gene is not allelic to the HO gene, which is responsible for previously described instances of homothallism in yeast. We have designated this new gene for homothallism as cmt (change of mating type).     

The uptake of sodium by perennial ryegrass and its relationship to potassium supply in flowing solution culture

Summary The uptake of Na and K by perennial ryegrass from flowing solution culture with monitored concentrations of Na and K was followed in two experiments. In the first, when only 50 and 10 per cent of the K uptake by one set of plants, grown with K held constant at 2.5 μeq 1⁻¹, was supplied to two other linked sets of plants and the balance supplied as Na, there was a rapid decrease in K, and an increase in Na, concentration in the shoots over a 20-day period. However, when compared with the plants grown in K in solution held constant, there was not a complete replacement of Na for K. In the second experiment the concentration of K in the culture solution was held constant at 2 μeq 1⁻¹ and Na at 0, 5, 25, 50 and 100 μeq 1⁻¹. Although uptake of Na increased with increasing concentration in solution the contents in the plants were low,i.e. less than 0.19 per cent and decreased with time. There was an increase in the yield of both shoots and roots with increasing Na in the solution; it was suggested that, during the early stages of growth there may have been an inadequate supply of K and that Na may have substituted for K in some of the non-specific roles of K in the plants. There was evidence in both experiments that a flux of H-ions was involved in the uptake of Na.     

The purification and properties of Escherichia coli methylglyoxal synthase

1. Methylglyoxal synthase was purified over 1500-fold from glycerol-grown Escherichia coli K 12 strain CA 244. The purified enzyme was inactivated by heat or proteolysis, had a molecular weight of approx. 67000, a pH optimum of 7.5 and was specific for dihydroxyacetone phosphate with K(m) 0.47mm. 2. The possibility that a Schiff-base intermediate was involved in the reaction mechanism was investigated but not confirmed. 3. The purified enzyme lost activity, especially at low temperature, but could be stabilized by P(i). Two binding sites for P(i) may be present on the enzyme. Of other compounds tested only the substrate, dihydroxyacetone phosphate, and bovine serum albumin showed any significant stabilizing effect. 4. Phosphoenolpyruvate, 3-phosphoglycerate, PP(i) and P(i) were potent inhibitors of the enzyme. Kinetic experiments showed that PP(i) was apparently a simple competitive inhibitor, but inhibition by the other compounds was more complex. In the presence of P(i) the enzyme behaved co-operatively, with at least three binding sites for dihydroxyacetone phosphate. 5. It is proposed that methylglyoxal synthase and glyceraldehyde 3-phosphate dehydrogenase play important roles in the catabolism of the triose phosphates in E. coli. Channelling of dihydroxyacetone phosphate via methylglyoxal would not be linked to ATP formation and could be involved in the uncoupling of catabolism and anabolism.