The Immunoglobulin Response in Intact and Splenectomized Calves Infected with Anaplasma Marginale

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Abstract
Summary: Two groups of 4-month-old calves (group I intact, group II splenectomized) were infected with Anaplasma marginale. The kinetics of the immunoglobulin response throughout anaplasmosis were assayed by means of the radial diffusion test. In group I, IgM levels increased about 7 days before the onset of patent infection and reached a peak of 200% above the preinfection value for the group. This macroglobulinemia persisted for a long period. Concentrations of IgG increased 11 days after the initial increase in IgM, but the IgG response was neither pronounced nor prolonged. All the calves in group II died. In these, both the IgM and complement-fixing antibody responses were significantly delayed, although some of them synthesized appreciable amounts of IgM before death. It was postulated that enhanced severity of anaplasmosis in splenectomized animals resulted from, 1) decreased sensitivity to low levels of parasite antigens, leading to delayed antibody synthesis and 2) impaired phagocytosis of anaplasma, due to the absence of splenic reticuloendothelial system.