Immunoglobulin diversity, B-cell and antibody repertoire development in large farm animals.

The B-cell lineage, the antibodies produced by these cells and the diversification of the antibody repertoire are essential for the health and survival of all mammals. Cattle, sheep, swine and horses, unlike rodents and primates, develop their antibody repertoire from a relatively small number of VH (variable heavy) genes of one or several families and cattle, sheep and horses use almost exclusively lambda-light chains. These large farm animals appear to use templated mutation (gene conversion) in addition to untemplated (point) mutation in repertoire development; this may occur predominantly in the ileal Peyer's patches. Whether B-cell lymphogenesis is continuous throughout life--as in rodents and primates--or whether B cells are largely of the B-1 lineage and develop only in foetal and neonatal life, is uncertain. The fact that immunoglobulin D (IgD) is totally absent from swine and ruminants may be significant, as IgD is expressed weakly on rodent B-1 cells. Information on IgG subclass diversity in large farm animals is incomplete, except for sheep and cattle, and no information is available for any large farm animal to show whether T helper 1 (Th1) and Th2 responses correlate with the expression of any subclass antibody response, as is the case in rodents. All large farm animals exclusively use the mammary gland to transfer immunity to offspring, although the receptor involved in the transport of IgG into colostrum and milk has not been characterised. Efforts to standardise the nomenclature and measurements of antibodies and immunoglobulins in large farm animals are discussed, and a proposal currently under review concerning the standardisation of the nomenclature for bovine immunoglobulins is presented as a model.