Componentes imunológicos do colostro bovino: células, teores de imunoglobulinas e atividade bactericida dos fagócitos para a Escherichia coli enterotoxigênica (ECET) / Immunological components of bovine collostrum: cells, immunoglobulin content and bactericidal activity of phagocytes against enterotoxigenic Escherichia coli

AUTOR(ES)
DATA DE PUBLICAÇÃO

2008

RESUMO

Bovine collostrum citology, immunoglobulin content and bactericidal activity of phagocytes against enterotoxigenic Escherichia coli were studied qualitatively and quantitatively, analyzing the influence of previous opsonization of the bacterium. In order to achieve this aim, 53 Holstein cows were used to obtain 212 collostrum samples before the first and second milkings. Samples positive (n=41) in the bacteriological examination of milk were excluded from the trial. Direct microscopy and cytocentrifugation were used in the quantitative and qualitative cytological analysis of collostrum, respectively. Immunoglobulin (IgG, IgM and IgA) contents were determined by means of radial immunodiffusion using commercial kits. Indirect bactericidal activity of phagocytes and assessment of the influence of ETEC previous opsonization were carried out as follows: using only a suspension of mononuclear and polymorphonuclear phagocytes in culture medium (Control group - C); suspension of mononuclear and polymorphonuclear phagocytes added to a suspension of non-opsonized ETEC (NO group); suspension of mononuclear and polymorphonuclear phagocytes added to an ETEC suspension previously opsonized with 10% of supernatant of delipidated bovine collostrum (O group). Indirect bactericidal activity of phagocytes was measured by means of the amount of hydrogen peroxide nmoles released by these cells in assays C, NO and O. After results were evaluated, it was concluded that: (1) bovine collostrum obtained in the second milking showed more cells/mL than first milking collostrum; (2) the predominance of mononuclear cells was determined by both direct microscopy and cytocentrifugation; (3) bovine collostrum obtained in the second milking showed greater quantity of polymorphonuclear neutrophils than that of the first milking, as determined in cell type counts by direct microscopy and cytocentrifugation; (4) cell types predominating in bovine collostrum of the first and second milking were macrophages / epithelial cells, followed by lymphocytes, neutrophils and eosinophils, respectively, using cytocentrifugation for cell differentiation; (5) first milking bovine collostrum showed greater levels of immunoglobulins G and M than that of the second milking, with a predominance of IgG compared with IgM and IgA, no matter the milking order; (6) phagocytes in first milking collostrum showed greater cell activity than those in the second milking collostrum, as evaluated by hydrogen peroxide release; (7) antigenic stimulation of ETEC was not enough to increase bactericidal activity of phagocytes in bovine collostrum; (8) ETEC opsonization with collostral serum did not lead to significant differences in bactericidal activity of bovine collostrum phagocytes, as measured by the amount of hydrogen peroxide released by these cells; (9) there was a positive correlation between the contents of immunoglobulin M and the amount of hydrogen peroxide released by phagocytes in bovine collostrum; (10) quantitative behavior observed for immunoglobulins and cells of bovine collostrum considering the milking order, suggest that antibodies would have a essential function in neonate immunity, whereas the increase in neutrophils would apparently be linked to mammary gland protection.

ASSUNTO(S)

cytology bovine imunoglobulinas phagocytes bovino fagócitos colostro collostrum citologia immunoglobulins

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