Colostrogenesis: IgG1 Transcytosis Mechanisms

Abstract

Biological transport of intact proteins across epithelial cells has been documented for many absorptive and secretory tissues. Immunoglobulins were some of the earliest studied proteins in this category. The transcellular transport (transcytosis) of immunoglobulins in neonatal health and development has been recognized; the process is especially significant with ungulates because they do not transcytose immunoglobulins across the placenta to the neonate. Rather, they depend upon mammary secretion of colostrum and intestinal absorption of immunoglobulins in order to provide intestinal and systemic defense until the young ungulate develops its own humoral defense mechanisms. The neonatal dairy calf's ability to absorb immunoglobulins from colostrum is assisted by a ~24 h "open gut" phenomenon where large proteins pass the intestinal epithelial cells and enter the systemic system. However, a critical problem recognized for newborn dairy calves is that an optimum mass of colostrum Immunoglobulin G (IgG) needs to be absorbed within that 24 h window in order to provide maximal resistance to disease. Many calves do not achieve the optimum because of poor quality colostrum. While many studies have focused on calf absorption, the principal cause of the problem resides with the extreme variation (g to kg) in the mammary gland's capacity to transfer blood IgG1 into colostrum. Colostrum is a unique mammary secretory product that is formed during late pregnancy when mammary cells are proliferating and differentiating in preparation for lactation. In addition to the transcytosis of immunoglobulins, the mammary gland also concentrates a number of circulating hormones into colostrum. Remarkably, the mechanisms in the formation of colostrum in ungulates have been rather modestly studied. The mechanisms and causes of this variation in mammary gland transcytosis of IgG1 are examined, evaluated, and in some cases, explained.

Iodine supplementation of the pregnant dam alters intestinal gene expression and immunoglobulin uptake in the newborn lamb

“…Maternal iodine supplementation altered the expression of B2M, PIGR and MYC in the neonatal lamb. Previous physiological studies have associated these genes with intestinal immunoglobulin (Ig) transfer (Bruno et al, 2004;Baumrucker and Bruckmaier, 2014). It is evident also that THRB expression at the newborn intestinal level is diminished following maternal prepartum supplementation (CaIO 3 ) in conjunction with reduced free T 3 concentrations in these animals.…”

“…At birth, the ruminant intestinal tract is undergoing a maturational process in preparation for colostrum ingestion and absorption before gut closure. Due to the requirement for B2M in the maturation and functioning of FcRn (Baumrucker and Bruckmaier, 2014) and the increased relative expression of B2M in the ileum of CaIO 3 lambs at 1 h postpartum it was concluded that iodine supplementation of the dam has no negative influence on the functioning of the FcRn receptor. Additionally, the lower expression of PIGR and increased serum IgG in non-supplemented progeny is in agreement with Johansen et al (1999) who found that PIGR knockout mice had increased levels of serum IgG in comparison to PIGR abundant mice.…”

Comparison of single radial immunodiffusion and ELISA for the quantification of immunoglobulin G in bovine colostrum, milk and calf sera

“…However, it is an expensive and time-consuming test, requiring an incubation period of 18-24 h. In contrast, ELISA method has a higher throughput, is less costly and analysis can be completed in a much shorter time (Lee et al 2008). Consequently, recent research has used ELISA method to quantify IgG levels in colostrum, plasma and sera (Vetter et al 2013;Baumrucker and Bruckmaier 2014;Gelsinger, Smith, et al 2015).…”

Changeover from signalling to energy-provisioning lipids during transition from colostrum to mature milk in the giant panda (Ailuropoda melanoleuca)

“…Mammary secretions change dramatically from colostrum (‘first milk’) to mature, main-phase milk during the immediate post-partum period. Broadly, colostrum tends to be more protein-rich and lipid-poor than later milk, and is particularly rich in immunoglobulins and innate anti-microbial factors1234567. The change to mature milk represents a switch to more energy-rich nutrition in which sugars and fats may predominate12.…”

“…At the other extreme are species with haemochorial placentae (e.g. humans) whose placentae transport immunoglobulins from maternal to foetal blood circulations prior to birth, although this is confined to immunoglobulin G (IgG)234.…”