Tumor protein D52 (TPD52): A novel B-cell/plasma-cell molecule with unique expression pattern and Ca2+-dependent association with annexin VI

We generated a murine monoclonal antibody (B28p) detecting an antigenic determinant shared by the immunoglobulin superfamily receptor translocation-associated 1 (IRTA1) receptor (the immunogen used to raise B28p) and an unrelated 28-kDa protein that was subsequently subjected to extensive characterization. The expression of the 28-kDa protein in normal lymphohematopoietic tissues was restricted to B cells and plasma cells and clearly differed from that expected for IRTA1 (selectively expressed by mucosa-associated lymphoid tissue [MALT] marginal zone B cells). Two-dimensional polyacrylamide gel electrophoresis (2D-PAGE)/mass-spectrometry analysis identified the 28-kDa protein as human tumor protein D52 (TPD52), whose expression had been previously described only in normal and neoplastic epithelia. Specific B28p reactivity with TPD52 was confirmed by immunostaining/immunoblotting of TPD52-transfected cells. TPD52 expression pattern in normal and neoplastic B cells was unique. In fact, unlike other B-cell molecules (paired box 5 [PAX5], CD19, CD79a, CD20, CD22), which are down-regulated during differentiation from B cells to plasma cells, TPD52 expression reached its maximum levels at the plasma cell stage. In the Thiel myeloma cell line, TPD52 bound to annexin VI in a Ca2+-dependent manner, suggesting that these molecules may act in concert to regulate secretory processes in plasma cells, similarly to what was observed in pancreatic acinar cells. Finally, the anti-TPD52 monoclonal antibody served as a valuable tool for the diagnosis of B-cell malignancies

Quantitative determination of mammary tumor virus in individual samples of mouse milk.

The possibility to determine quantitatively the intact mammary tumor virus (MTV) in milk of mice carrying milk-transmitted MTV has been assayed by a method that allows direct comparison between individual milk samples. The method is based on (a) the measure of light scattering of partially purified MTV preparations, (b) the use of milk from genetically identical MTV free mice as blank and (c) the quantitative reference to the total protein content of whole milk. The sensitivity, specificity and reproducibility of the procedure, as well as the requirement of appropriate quantitative references, are illustrated and discussed. BALB/c (MTV free), BALB/cfC3H, and BALB/cfRIII mice have been used

Quantitative determination of mammary tumor virus in individual samples of mouse milk

The possibility to determine quantitatively the intact mammary tumor virus (MTV) in milk of mice carrying milk-transmitted MTV has been assayed by a method that allows direct comparison between individual milk samples. The method is based on (a) the measure of light scattering of partially purified MTV preparations, (b) the use of milk from genetically identical MTV free mice as blank and (c) the quantitative reference to the total protein content of whole milk. The sensitivity, specificity and reproducibility of the procedure, as well as the requirement of appropriate quantitative references, are illustrated and discussed. BALB/c (MTV free), BALB/cfC3H, and BALB/cfRIII mice have been used