Issue |
Vet. Res.
Volume 34, Number 5, September-October 2003
Mastitis of dairy ruminants
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Page(s) | 647 - 670 | |
DOI | https://doi.org/10.1051/vetres:2003025 | |
How to cite this article | Vet. Res. (2003) 647-670 |
DOI: 10.1051/vetres:2003025
The complement in milk and defense of the bovine mammary gland against infections
Pascal RainardLaboratoire de Pathologie Infectieuse et Immunologie, Institut National de la Recherche Agronomique, 37380 Nouzilly, France
(Received 28 October 2002; accepted 13 January 2003)
Abstract
The mammary gland of dairy cows, which is prone to infection by various bacteria,
mobilizes local and systemic immune defenses to cope with pathogens. The complement system
plays an important part in the innate immunity against microorganisms through its bactericidal,
opsonic, and phlogistic functions. The amount of the complement in the milk of healthy glands of
dairy cows is low. Moreover, the classical pathway of activation is not functional because of a
shortage in C1q. By contrast, the alternative pathway is active, deposits C3b and C3bi on bacteria,
and generates amounts of C5a which are highly variable among cows. A slight inhibition of the
bactericidal/hemolytic activities, of the deposition of C1q on bacteria, and of the phlogistic activity
of C5a makes milk a rather anti-inflammatory fluid. The inhibitory activity does not involve C3b/
C3bi deposition on bacteria, nor the generation of C5a by the alternative pathway. When
inflammation develops, the blood-derived complement components overcome the inhibitions and
complement-dependent bactericidal, opsonic and phlogistic activities may be high in milk. Further
research is necessary to evaluate the contribution of C5a to the recruitment of leukocytes in the
mammary gland, and to specify the links between the complement system and the response of
resident cells (leukocytes and mammary epithelial cells) to infection stimulus. This will help to
define the contribution of the complement system to resistance against mastitis, and could help to
differentiate animals more or less resistant to this frequent and costly disease.
Key words: complement / milk / mastitis / dairy cattle / inflammation
Correspondence and reprints: Pascal Rainard rainard@tours.inra.fr
© INRA, EDP Sciences 2003