The search for a Potential Novel Receptor for Human Transferrin on APCs

Abstract

It is canonically known that Dendritic Cells (DCs) can activate T cells through its peptide-MHC binding to the T cell receptor (signal 1), in addition to its CD80/86 binding to CD28 on the T cell (signal 2). To facilitate this process, antigens undergo processing and presentation in DCs which then present linear peptides from the original protein antigen on MHC molecules. On the other hand, the ability of DCs to activate B cells has been studied less extensively. B cells, unlike T cells, are activated through direct recognition of specific epitopes on the antigen by the BCR. Based on prior data obtained in the laboratory, murine DCs appear to have a specific receptor for the display of HSA (human serum albumin); this receptor does not bind efficiently to bovine serum albumin (BSA). For the purposes of my thesis, I will be investigating the possible existence of a novel receptor that can present human transferrin to B cells. I show through flow cytometry that there is variation in the display of human transferrin on the surface of different immune cell subsets in the mouse spleen. I also show a high level of capture and display of human transferrin on the human B cell line BJAB, RAMOS and on a macrophage cell line. Preliminary data suggests that the distribution of CD71 and the receptor for display of human transferrin broadly but not completely overlap. Additionally, blocking experiments of CD71 were conducted and they showed that the blocking antibody is working properly and the data implies that a novel receptor exists. However, further data is needed before confirming these statements about the presence of a novel receptor.