A new monoclonal anti-CD7 antibody reactive on paraffin sections

CBC.37 monoclonal antibody (mAb) was generated using balb/c mice immunized with CEM T cell line. It was selected because of its strong reactivity on T lymphocytes on paraffin tissue sections. The anti-CD7 specificity of CBC.3 7 mAb was assessed by immunohistochemistry, cross-blocking, and cross-immun oprecipitation experiments using CBC.37 and the anti-CD7 mAb DK24. CBC.37 m Ab immunoprecipitated a 40-kDa. protein. Cross-blocking and cross-immunopre cipitation experiments demonstrated that the two antibodies recognized the same molecule. Immunostaining of a large number of reactive lymph nodes and B and T cell lymphomas confirms that CBC.37 mAb was directed against T cel ls. As expected, on reactive lymph nodes the staining pattern was comparabl e to that of CD3. Among the 110 T cell lymphomas examined all T lymphoblast ic lymphomas were positive (15+115; 100%). As a result of the frequent loss of CD7 antigen, only 25+/95 (26%) of peripheral T cell neoplasms were foun d to be positive for CBC.37. A marked reduction in the number of CBC.37-pos itive T cells was observed in 7 of the 60 cases of benign inflammatory derm atoses studied (approximate to 12%). CBC.37 was unreactive with all healthy and neoplastic non-lymphoid samples examined. Because the lack of CD7 expr ession in T cell lymphomas is of diagnostic value, CBC.37 mAb in associatio n with other anti-T cell antibodies working on paraffin sections could be o f particular value in asserting the diagnosis of T cell lymphomas in routin e histopathology.