IMMUNOGLOBULIN METABOLISM IN SHEEP INFECTED WITH THE SMALL INTESTINAL NEMATODE TRICHOSTRONGYLUS COLUBRIFORMIS

Abstract

Summary Radiotracer techniques were used to compare the kinetics of IgG1 and IgG2 metabolism in sheep (1) prior to parasite exposure, (2) during an initial patent infection with Trichostrongylus colubriformis, and (3) during continuous exposure to the parasite when the animals were exhibiting resistance. Plasma concentrations of IgG1, IgG2, IgA and IgM were also monitored throughout the experiment. Plasma IgG1 concentration increased significantly during the development of resistance and maintained this higher level on further exposure to the parasite. IgA concentration was also elevated during the development of resistance to a level approximately three times that observed prior to initial infection, hut this increase was only transitory. No significant changes in either IgG2 or IgM concentration occurred. Analysis of the radiotracer data for IgG1 and IgG2, was based on a two‐compartment model comprising intravascular and extravaseular protein pools with reversible exchange between them and irreversible loss from the intravascular site. No significant changes in compartment sizes or rates of exchange between compartments were recorded during measurement periods (1), (2) and (3) for either IgG1 or IgG2. Rates of irreversible loss of IgG2 were similar during (1), (2) and (3); the irreversible loss of IgG1 was unaltered following the initial infection but Increased by approximately 50% during period (3). It is concluded that increased synthesis of IgG1 in resistant sheep continually exposed to T. colubriformis occurs as a result of antigenic stimulation rather than as a consequence of increased loss of plasma into the intestine.

The effect of vaccinating infection during pregnancy and dietary protein supply on the peri-parturient immune response of sheep to infection with Teladorsagia circumcincta and Trichostrongylus colubriformis larvae

“…In animals with no previous exposure a nonspecific recruitment in mucosal tissues of eosinophils and production of IgA antibody is followed by increases in MMC and their de-granulated cell remnant, GL (Huntley et al, 1984;Pfeffer et al, 1996). Subsequently, EOS recruitment to tissue and antibody production diminish, a pattern which has been observed in peripheral EOS numbers (Kimambo et al, 1988) and IgA antibodies (Cripps and Steel, 1978;Henderson and Stear, 2006). Balic et al (2000) interpreted changes in EOS numbers as indicating recruitment to mucosal tissue until the components of the mature protective immune armoury are able to exclude larvae from mucosal tissue.…”

“…Balic et al (2000) interpreted changes in EOS numbers as indicating recruitment to mucosal tissue until the components of the mature protective immune armoury are able to exclude larvae from mucosal tissue. Circulating concentrations of antibodies have been shown to be highly correlated with rates of antibody production (Cripps and Steel, 1978) though the sensitivity of peripheral IgA to small changes in production in mucosal tissue is unclear (Sinski et al, 1995;Henderson and Stear, 2006). The ubiquitous increase in IgA in peripheral circulation during the acquisition of immunity in naïve animals and its subsequent decline (Cripps and Steel, 1978;Henderson and Stear, 2006) and the lack of peripheral response in animals with established immunity (Greer et al, 2005) suggests that, like eosinophils, its rate of production in mucosal tissues, and therefore appearance in circulation, may reflect the extent of larval penetration of the tissue determined by the effectiveness of the mature mucosal-cell based immune response.…”

“…Circulating concentrations of antibodies have been shown to be highly correlated with rates of antibody production (Cripps and Steel, 1978) though the sensitivity of peripheral IgA to small changes in production in mucosal tissue is unclear (Sinski et al, 1995;Henderson and Stear, 2006). The ubiquitous increase in IgA in peripheral circulation during the acquisition of immunity in naïve animals and its subsequent decline (Cripps and Steel, 1978;Henderson and Stear, 2006) and the lack of peripheral response in animals with established immunity (Greer et al, 2005) suggests that, like eosinophils, its rate of production in mucosal tissues, and therefore appearance in circulation, may reflect the extent of larval penetration of the tissue determined by the effectiveness of the mature mucosal-cell based immune response. The present sheep would have been expected to have had an established immunity to the nematode species used as a consequence of an inevitable exposure to larvae of these nematodes which are endemic in the farm environment in which they had been reared.…”