Last month, an article in a journal of the American Chemical Society reviewed the literature for this association:
Relation of Time of Introduction of Cow Milk Protein to an Infant and Risk of Type-1 Diabetes Mellitus, Journal of Proteome Research, April, 2008
It's author, Marcia Goldfarb, described a set of conditions which could explain how pancreatic beta cells are destroyed - leading to type 1 diabetes - when cow's milk products are fed to infants:
"The newborn intestine does not have complete "closure" and can pass food antigens. Beta Lactoglobulin could generate antibody to glycodelin undermining T cell regulation of beta cells."
- Beta-lactoglobulin is a protein present in cow's milk, but not human milk. "It has the largest concentration of any whey protein in bovine milk. (Goldfarb)" Glycodelin is a human protein that affects our immune system, regulating our T-cells.
- The cow beta-lactoglobulin and the human glycodelin have similar structures, such that an infant's body may generate antibodies not just for the foreign beta-lactoglobulin, but also for the endogenous glycodelin.
- Type 1 diabetes is thought to be caused by autoimmune destruction of pancreatic beta cells by T-cells. Destruction of glycodelin (by the antibodies generated to destroy the foreign cow's milk protein) may allow proliferation of these beta-cell-destroying T-cells.