Conglutinin, collectin-43 (CL-43) and collectin-46 (CL-46) are serum proteins characteristic for Bovidae. They belong to collectins--family of oligomeric proteins composed of trimeric subunits containing collagen-like sequences joined to C-type lectin domains. The genes encoding conglutinin, CL-43 and CL-46 are located on the bovine chromosome 28, and phylogenetic analysis indicates their common origin--from the lung surfactant protein D gene. Northern blot or immunocytochemical analysis confirm biosynthesis of bovine collectins mainly in the liver (conglutinin, CL-43) and in the thymus (CL-46). The level of conglutinin in the serum of dairy cows depends on many factors such as breeding, the season of the year, the stage of the reproductive cycle and infection. The collectins are involved in the innate immune defense. They bind to microbial surface carbohydrates inducing aggregation and, thereby, impeding infectivity. On the other hand the destruction of pathogens occurs due to stimulation of effector cells. CL-43 as well as conglutinin, binds to the collectin receptor (C1qR) localized on many types of cells identified as a surface variant of calreticulin. Conglutinin and CL-43 show antiviral activities towards influenza A virus and rotaviruses. Conglutinin also displays protective activity against bacterial infections.