Background：cells and B cells are activated. It was reported that CD44 is a valuable marker for memory T cells. CD44 is an adhesion molecule involved in leukocyte adhesion and homing to lymphoid organs. The OX-49 antibody reacts with CD44H （known as CD44s） expressed most leukocytes, except for a subset of B lymphocytes. The epitope recognized by OX-49 antibody has been mapped to a region on both the standard, CD44s, and the splice variant, CD44v, isoforms of CD44. However it was reported that OX-49 antibody cannot detect the CD44V isoform, possibly due to conformational changes in the epitope
