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The turnover rate and pool volume of radiolabelled autologous IgG1 was similar to homologous IgG1 in adult sheep. In neonatal lambs there was no significant difference for either of these parameters between homologous serum IgG1 and maternal colostrum IgG1. However, the pool volume for IgG1 expanded by approx. 30% over the experimental period in the lambs. When the turnover rates were corrected for this increase they were found to be similar to those observed for IgG1 in adult animals.

The experiment comprised two sections. First, radiotracer techniques were used to study the metabolism of IgG1 and IgG2 in 5 non-pregnant and 4 pregnant ewes. In the pregnant ewes, the rates of synthesis for IgG1 and IgG2 were similar to the rates observed in non-pregnant animals. However, the irreversible loss of IgG1 was significantly greater than IgG2 in pregnant ewes and IgG1 in non-pregnant ewes. Additionally, it was found that most of the IgG1 and virtually all of the IgG2 in mammary secretion was serum derived. Secondly, the levels of sodium, potassium and lactose and the selective index for IgG1 in mammary secretions of 5 pregnant ewes were monitored over the parturient period. The values of all the measures remained relatively constant until one day before parturition. From one day pre-partum, the levels of potassium and lactose in mammary secretion began to increase and had risen 2-3 fold by 5 days post-partum. Over the same period, the selective index for IgG1 decreased 20 fold, wehreas the level of sodium fell from approximately 32 mmol/l to 18 mmol/l. The concentration of IgG1 in plasma slowly declined from approximately 23 g/l to 15 g/l over the last 10 days of pregnancy. During the parturient period, the decline in plasma IgG1 levels, in comparison with IgG2, without alteration in the rates of synthesis of either immunoglobulin, supports the hypothesis that selective transport of IgG1 into mammary secretion occurs without degradation. The results also indicate that the transport of sodium and potassium into mammary secretions are altered over the parturient period.

A comparison was made of the antibody-containing cell (ACC) response in hepatic and intestinal lymph of sheep following intraperitoneal injection of ovalbumin in Freund's complete adjuvant (FCA), Freund's incomplete adjuvant (FIA) or the bland vegetable oil preparation, adjuvant 65. There was a substantial ACC response in intestinal lymph following intraperitoneal injection of ovalbumin in either FCA or FIA. Responses were essentially similar in magnitude and for both adjuvants ACC were distributed mainly among the IgGl, IgA and IgM immunoglobulin classes. In contrast, there was a negligible ACC response in intestinal lymph following injection of antigen in adjuvant 65. The output of ACC in hepatic lymph and the immunoglobulin class distribution of the ACC following intraperitoneal injection of antigen in either FCA or FIA were similar and results were specificity comprising 32% of ACC at the peak of the response. In contrast to results for intestinal lymph, injection of antigen in IgGl- and IgM-specific cells in hepatic lymph. The ACC response was much smaller in magnitude than with the Freund's adjuvants. Intravenous injection of ovalbumin in FIA or adjuvant 65 gave rise to substantial ACC responses in hepatic lymph which contrasted with the barely detectable response in intestinal lymph. Following intravenous administration the great majority of ACC in hepatic lymph were of the IgM class irrespective of adjuvant used although ACC of the IgA class made a transitory appearance.

The aim of the present study was to develop an immunization procedure which centrally stimulated the IgA system of sheep with the release of antibody-containing cells (ACC) of the IgA class into intestinal lymph. It was found that intraperitoneal injection of ovalbumin resulted in a substantial output of ACC in intestinal lymph. ACC of the IgA class reached a peak 8--9 days after intraperitoneal injection when they comprised 1.4% of cells in lymph. ACC of the IgM and IgG1 classes comprised 3.5 and 2.9% of cells in lymph at this time. The output of ACC of the IgA, IgM and IgG1 classes in lymph at the peak of the response was respectively, 3.7 X 10(6), 9.8 X 10(6) and 8 X 10(6) cells/h. In marked contrast to rats, virtually no ACC appeared in intestinal lymph of sheep following intraduodenal infusion of ovalbumin in animals primed 2 weeks earlier by intraperitoneal injection of antigen in Freund's complete adjuvant (CFA).

A comparative study was made on the secretion of IgG1 and IgA into parotid and submaxillary saliva of sheep. The purpose of the study was to examine the suggestion that in the external secretory organs of ruminants there is an inverse relationship between the capacity to selectively transfer IgG1 and the development of the IgA secretory system. Despite a marked difference in the secretion of IgA between the parotid and submaxillary salivary glands, the magnitude of selective transfer of IgG1 was similar. Thus, there appears to be no relationship between the selective transfer of IgG1 and the secretion of IgA into the saliva of sheep.