Summary and Explanation:
CD5 is a T-cell associated marker that is also expressed by two B-cell neoplasms; lymphocytic leukemia and mantle cell lymphoma. CD5 antigen is expressed in 95% of thymocytes and 72% of peripheral blood lymphocytes. In lymph nodes, CD5 is mainly reactive with Tcells. It has been shown to react with thymic carcinomas, but rarely in thymomas. It has also been observed in a subset of intravascular large B-cell lymphomas and marks some anaplastic large cell lymphomas. CD5 has proven very useful in marking mantle cell lymphoma when used in tandem with CD23, cyclin D1, and CD10 (CD10 is negative; CD5, cyclin D1 are positive for mantle cell lymphoma).
Principle of Procedure:
Antigen detection in tissues and cells is a multi-step immunohistochemical process. The initial step binds the primary antibody to its specific epitope. A secondary antibody may be applied to bind the primary antibody, followed by an enzyme labeled polymer;
or an enzyme labeled polymer may be applied directly to bind the primary antibody. The detection of the bound primary antibody is evidenced by an enzyme-mediated colorimetric reaction.