Abstract: Compositions and methods for making complex carbohydrates in a bacterial production cell are disclosed. The complex carbohydrates that can be made include oligosaccharides and polysaccharides of bacterial or mammalian origin.

Abstract: Methods for inducing T cell tolerance to a tissue or organ graft in a transplant recipeint are disclosed. The methods involve administering to a subject: 1) an allogeneic or xenogeneic cell which expresses donor antigens and which has a ligand on the cell surface which interacts with a receptor on the surface of a recipient T cell which mediates contact-dependent helper effector function; and 2) an antagonist of the receptor which inhibits interaction of the ligand with the receptor. In a preferred embodiment, the allogeneic or xenogeneic cell is a B cell, preferably a resting B cell, and the molecule on the surface of the T cell which mediates contact-dependent helper effector function is gp39. A preferred gp39 antagonist is an anti-gp39 antibody. The allogeneic or xenogeneic cell and the gp39 antagonist are typically administered to a transplant recipient prior to transplantation of the tissue or organ.