The percentage of T- and B-cells in the lymphomyeloid tissue of hyperimmunized bursaless chickens

The impacts of body mass on immune cell concentrations in birds

Body mass affects many biological traits, but its impacts on immune defences are fairly unknown. Recent research on mammals found that neutrophil concentrations disproportionately increased (scaled hypermetrically) with body mass, a result not predicted by any existing theory. Although the scaling relationship for mammals might predict how leucocyte concentrations scale with body mass in other vertebrates, vertebrate classes are distinct in many ways that might affect their current and historic interactions with parasites and hence the evolution of their immune systems. Subsequently, here, we asked which existing scaling hypothesis best-predicts relationships between body mass and lymphocyte, eosinophil and heterophil concentrations-the avian functional equivalent of neutrophils-among more than 100 species of birds. We then examined the predictive power of body mass relative to life-history variation, as extensive literature indicates that the timing of key life events has influenced immune system variation among species. Finally, we ask whether avian scaling patterns differ from the patterns we observed in mammals. We found that an intercept-only model best explained lymphocyte and eosinophil concentrations among birds, indicating that the concentrations of these cell types were both independent of body mass. For heterophils, however, body mass explained 31% of the variation in concentrations among species, much more than life-history variation (4%). As with mammalian neutrophils, avian heterophils scaled hypermetrically (b = 0.19 ± 0.05), but more steeply than mammals (approx. 1.5 ×; 0.11 ± 0.03). As such, we discuss why birds might require more broadly protective cells compared to mammals of the same body size. Overall, body mass appears to have strong influences on the architecture of immune systems.

Characterization of a novel monoclonal antibody, EIV-E12, raised against enriched splenic ellipsoid-associated cells

A monoclonal antibody, EIV-E12, was produced against ellipsoid-associated cells. In postnatal chicks, the antigen defined by EIV-E12 associated with about 90% of bursal cells and accumulated in B cell-rich areas of lymphoid organs. The antigen was expressed by many splenic cells on day 9 of embryogenesis and about 1 day later in the bursal anlage, where the cells positive for the antigen localized in close proximity to the plical epithelium. In the bursa, these early EIV-E12 cells appeared before Bu-1-positive cells and may represent a dendritic cell precursor. B cells within the developing bud acquired the EIV-E12 antigen. Immunoprecipitation studies revealed a molecular weight of 233 (nonreduced) and 205 (reduced) for the EIV-E12 antigen. These values were markedly different from the molecular weight of the antigen identified by Bu-1 but similar to that of a CB10 antigen. The CB10 and EIV-E12 MAbs exhibited some differences in cellular staining. Taken together these data suggest that EIV-E12 MAb recognizes a unique cellular population during embryogenesis.