This rabbit monoclonal antibody reacts with the intracytoplasmic portion of the CD3 antibody antigen expressed by T cells. Studies have shown that CD3 stains human T-cells in both the cortex and medulla of the thymus and in peripheral lymphoid tissues. It does not react with B-cells, monocytes, granulocytes and platelets. CD3 is regarded as a reliable pan T-cell antibody used in the immunophenotyping of T-cell lymphomas in paraffin sections with the majority of T-cell lymphomas expressing positivity for CD3. When used in conjunction, CD3 and UCHL-1 together identified the vast majority of T-cell lymphomas in paraffin sections.