CD 19

Accurate (B19, CLB/B4/1, FMC63, polyclonal), Becton Dickinson (SJ25C1), Biodesign (BC3), Biogenex (B4), Biosource (BC3, SJ25C1), Caltag Laboratories (SJ25C1), Coulter (B4), Cymbus Bioscience (RFB9, SJ25-C1), Dako (HD37), Immunotech (386.12, J4.119), Novocastra (4G7/2E, FMC63), Pharmingen (B43, HIB19), Sanbio/Monosan (SJ25C1), Seralab, Sigma Chemical (SJ25C1) and Zymed (SJ25-C1).

The majority of these antibodies are only applicable to cryostat sections, although they may be used in acetone-fixed cryostat sections and smears. They are not suitable for formalin-fixed, paraffin-embedded sections.

The CD 19 gene (along with CD 20 and CD 22) encodes transmembrane proteins with at least two extracellular immunoglobulin-like domains that are of vital importance to B-cell function (McMichael, 1987). Similar to the immunoglobulin genes, they are expressed in a lineage-specific and developmentally regulated manner (Kehrl et al, 1994). In normal cells, CD 19 antigen (90 kD polypeptide) is the most ubiquitously expressed protein in the B-lymphocyte lineage (Scheuermann & Racila, 1995). CD 19 expression is induced at the point of B-lineage commitment during the differentiation of the hemopoietic stem cell. Its expression continues through pre-B and mature B-cell differentiation, being downregulated during terminal differentiation into plasma cells. Furthermore, CD 19 expression is maintained in neoplastic B cells, enhancing its diagnostic usefulness. Since CD 19 is not expressed in pluripotent stem cells, it has become the target for a variety of immunotherapeutic agents (Scheuermann & Racila, 1995).

B43 monoclonal antibody recognizes the same surface epitope as several other anti-CD 19 monoclonal antibodies. Using clone B43 to test for CD 19 expression on 340 leukemias and 151 malignant lymphomas, Uckun et al (1988) showed CD 19 to be the most reliable B-lineage surface marker. The advantage of immunodetection of CD 19 expression is that B lineage leukemias and lymphomas rarely lose the epitope (Scheuermann & Racila, 1995). Furthermore, CD 19 is not expressed on myeloid, erythroid, megakaryocytic or multilineage bone marrow progenitor cells (Uckun et al, 1988).

Although most B cells carry the CD 19 antigen, the use of anti-CD 19 is restricted to cryostat sections and is therefore not helpful in routine diagnostic histopathology practice.

•Kehrl JH, Riva A, Wilson GL, Thevenin C 1994. Molecular mechanisms regulating CD19, CD29 and CD22 gene expression. Immunology Today 15: 432-436.

•McMichael AJ (ed) 1987: Leucocyte typing III, White Cell Differentiation Antigens. Oxford: Oxford University Press, 305.

•Scheuermann RH, Racila E 1995. CD 19 antigen in leukaemia and lymphoma diagnosis and immunotherapy. Leukemia and Lymphoma 18: 385-397. immunotherapy. Leukemia and Lymphoma 18: 385-397.

•Uckun FM, Jaszcz W, Ambrus JL et al 1988. Detailed studies on expression and function of CD 19 surface determinant by using B43
monoclonal antibody and the clinical potential of anti-CD19 immunotoxins. Blood 71: 13-29.

Manual of diagnostic antibodies for immunohistology / Anthony S.-Y. Leong, Kumarasen Cooper, F. Joel W.-M. Leong.