No abstract

Two-dimensional (2-D; Iso Dalt method) electrophoresis was done on lipid membrane fractions from human milk samples collected in polypropylene tubes at home by the mother. The samples represent milk from two weeks to ten months post partum. Identification was made by immunoassay of Western blots. Apolipoprotein E was not easily seen on silver-stained gels because concentration is small and spots overlap another protein. Blot assays show a more complex pattern than 34 kDa plasma apo E with molecular size isoforms at 36 kDa, 34 kDa, 20 kDa and 15 kDa. One sample was negative for apo E. Apo E plays an important role in lipid transport in tissue and in the brain. It is synthesized in a variety of tissues by specific cells. Milk may reflect several sources.

Several studies of infant feeding show a causal relationship between time of introduction of formula containing cow protein and risk of onset of type-1 diabetes mellitus. This paper cites the literature pro and con and discusses lipocalins which might play a role in the pathogensis. β Lactoglobulin, a major lipocalin protein in bovine milk, is homologous to the human protein glycodelin (PP14), a T cell modulator. Anti-β lactoglobulin cross-reacts with glycodelin. The newborn intestine does not have complete “closure” and can pass food antigens. β Lactoglobulin could generate antibody to glycodelin undermining T cell regulation of beta cells.

Identification of human milk proteins and formulation of a two-dimensional map is a first step in a project which intends to survey human milk proteins by two-dimensional electrophoresis. Thirty-four proteins have been identified using the Iso-Dalt method of separation and Western blot with immunoprobes. Identification confirms that milk is species-specific, and, therefore, breast feeding confers a decided advantage for the infant. Using antisera for identification has revealed relationships between molecules which have not been previously noted. The antibody recognizes a common epitope between the IgA alpha chain and lactoferrin, and between the IgD d chain and beta casein. Milk protein concentrations vary longitudinally, diurnally, and individually. Identification of the proteins contributes meaning to the varying patterns. Knowledge of human milk proteins will help to elucidate human nutrition and health needs.

Two-dimensional (2-D) electrophoresis was performed on 24 serum samples from patients diagnosed with monoclonal gammopathies. These samples had been shown to have a homogeneous immunoglobulin (M component) by zone electrophoresis and immunofixation. Using 2-D electrophoresis, the nature of this aberrant protein was further analyzed. It has been presumed that the sharp, dark stained band identified by immunofixation was the production of a monoclonal immunoglobulin. The increased resolution afforded by 2-D methodology reveals several different patterns. On 2-D electrophoresis, a monoclonal antibody has a unique pattern. It consists of 3 to 6 strong, restricted heavy chain bands and a single distorted light chain spot. The 3-6 bands are microheterogeneity of the isoelectric point, attributed to posttranslational glycosylation and/or amidation/deamidation. Analysis by 2-D electrophoresis indicated only 5 samples with a true monoclonal pattern. All but 2 of the samples clearly had aberrant immunoglobulin, but interpretation of the pattern would suggest the protein is other than a fully synthesized monoclonal antibody. The samples showed the following: a monoclonal heavy chain pattern with multiple distorted light chain spots, only an aberrant light chain area, only an aberrant heavy chain, and only a polyclonal increase. Several IgG gammopathies had, in addition, concentrations of gamma heavy chain at a reduced size (34 kDa).