Studies on the systemic availability of maternal and endogeneously produced immunoglobulin G1 and G2 in newborn calves by using newly developed ELISAsystems

The time course of serum concentrations of the bovine IgG1 and IgG2 was mon itored in 18 newborn colostrum-fed calves from birth ro 11 weeks of age. Ai l calves received three 1.51 meals of a pooled colostrum with IgG1 and IgG2 concentrations of 54.9 mg/ml and 4.2 mg/ml during the first 14 h post-natu m. The mean IgG concentrations in calf serum increased from 0.15 mg IgG1/ml and 0.06 mg IgG2/ml (precolostral values) to 9.3 mg IgG1/ml and 0.8 mg IgG 2/ml 12 h after the third colostrum meal. Thereafter, IgG1 decreased contin uously to a minimum level of 4.9 mg/ml (p < 0.05) at day 28 post-natum and increased to 9.0 mg/ml at day 77. Postcolostral mean IgG2 was lowest (0.5 m g/ml) at day 11 and highest (1.2 mg/ml) at day 77. With these postcolostral IgG concentrations the respective body weight-corrected serum IgG pools ap proximately were calculated. According to chat procedure the initially high IgG pool in the serum at day 2 corresponds to 11.3 and 8.7%, respectively, of the ingested colostral IgG1 and IgG2. The time course of these IgG pool s in the serum could be characterized by lour typical phases. After a rapid increase from 0.45 g to 22.6 g (12 h after thr last colostrum meal) in pha se I, the total serum IgG decreased to 17.6 g at day 11 post-natum (phase I I) and levelled-out until dav 28 post-natum at a value of 17.3 g (phase III ). In phase IV rural serum IgG increased to 49.3 g at the end of the observ ation period (week 11). Considering these IgG values, which had been standa rdized by body weight, the endogeneous IgG production seemed to start clear ly (at week 1-2 post-natum) before the increase of the IgG concentration in the serum. To measure these IgG1 and IgG2 concentrations in the serum as w ell as in the colostrum, sandwich ELISA detection systems were developed wh ich specifically quantify these IgG subclasses in cattle. The specific immu noglobulin Y (IgY) could be isolated from the egg yolk of laying hens which have been immunized with bovine IgG1 or IgG2 and 1.6% (IgG1) and 1.9% (IgG 2) of total egg yolk IgY were found to be subclass-specific after purificat ion. For the newly developed IgG2-specific sandwich ELISA system the subcla ss-specific IgY antibody was used for coating and peroxidase-marked protein G served as conjugate. Due to crossreactivity problems monoclonal antibodi es were used to develop a further sandwich ELISA for the quantification of IgG1. Both newly developed ELISA detection systems showed sufficiently high reproducibility and sensitivity for routine diagnostic purposes.