Camelid immunoglobulins and their importance for the new-born--a review.

Camelid immunoglobulins differ from all other known antibodies and contradict all common theories on antibody diversity. It was demonstrated that up to 75% of all serum proteins are immunoglobulin G (IgG) molecules lacking light chains. IgG2 and IgG3, which only consist of heavy chains, have a low molecular weight which improves their biodistribution and allows a better tissue penetration. Of special importance is the long complementary determining region (CDR) loop which inserts deep into the active site of an enzyme. This binding property was only observed in experiments to gain structural data and to point out the extraordinary value of heavy chain antibodies as biochemical and pharmacological tools. The acquisition and absorption of adequate amounts of colostral immunoglobulins are essential to the health of the neonate. Pre-colostrum serum IgG levels in camelids are low, with concentrations of 0.26 +/- 10.23 mg/ml. Maximum IgG levels are reached after 24 h and kept at a plateau with concentrations of 24.52 +/- 8.8 mg/dl. IgG concentrations above 10 mg/ml indicate a successful passive transfer. IgG levels decline after 2-5 weeks and a marked increase is observed between 1 and 2 months, indicating that the immune system of the neonate has started to mature. A number of different tests are available for the assessment of IgG serum levels. Single radial immunodiffusion (SRID) is the only method that specifically measures serum IgG concentrations. It is a reliable assay to test failure of passive transfer (FPT). FPT is a major factor in neonatal mortality in camelids, but very little has been published so far. Therapeutic administration of colostrum will provide passive protection against infectious diseases for a 2-3-week period of risk, and the intravenous administration of 20-40 ml of camelid plasma helps to combat FPT.