Michael J. Caulfield

Constitutive expression of the Wilms tumor suppressor gene (WT1) in renal cell carcinoma

The expression of the Wilms tumor suppressor gene WT1 is largely restricted to elements of the developing urogenital system. In the fetal kidney, WT1 transcripts are present at low levels in the condensing mesenchyme and at much higher levels in differentiating glomerular epithelium and are not detected in other mesenchymal‐derived epithelial structures such as the proximal and distal tubules. However, WT1 expression is observed in tubule‐like elements found in some Wilms tumors. As renal cell carcinoma (RCC) of the clear cell type is one of the most prevalent adult tumors of the kidney, and is thought to originate from the epithelial cells of the proximal tubules, we studied WT1 expression in RCCs. Despite the absence of WT1 in normal primary epithelial cells derived from proximal tubules, RCC tumors and tumor‐derived cell lines expressed WT1 RNA. Immunocytochemical analyses of tumor cryosections showed widespread expression throughout the poorly differentiated epithelial components of the tumor. Immunoblots of RCC samples detected a normal size WT1 protein and reciprocal antibody immunoprecipitations of RCC cell extracts indicated that WT1 interacts with p53 as has been demonstrated for normal human fetal kidney. The aberrant expression of functional WT1 in RCC may represent a reversion to a more de‐differentiated phenotype and may contribute to the tumorigenic phenotype by inappropriately activating or repressing genes involved in growth regulation. Int. J. Cancer 78:182–188, 1998.© 1998 Wiley‐Liss, Inc.

A computer program for the evaluation of ELISA data obtained using an automated microtiter plate absorbance reader

A new computer program is described which calculates titers and antibody concentrations from ELISA data. Optical densities are measured in 96-well microtiter plates using an automated colorimeter and simultaneously fed into a microcomputer. The data can then be arranged and printed in an 8 X 12 format corresponding to the format of a 96-well microtiter plate. The computer program can also compute the titers of samples if the samples are arranged and titrated in one of the suggested formats. In addition, the titers of unknown samples can be automatically compared with the titer of a standard to obtain concentrations. An ELISA designed to measure the concentration of murine antibodies to the cell wall polysaccharide (PnC) extracted from Streptococcus pneumoniae was performed to document the use of the program.

Idiotype-restricted antibody response to specific immune complexes

In this report, we compared the immunogenicity of specific antigen/antibody complexes with that of free antigen. The complexes were prepared in antigen excess using the TEPC-15 myeloma protein and a phosphorylcholine-containing polysaccharide antigen (PnC), and the PnC-specific antibody response was measured using a hemolytic plaque assay 5 days after immunization. The results showed that the complexes were as immunogenic as the free antigen; however, the PnC-specific antibody response induced with the complexes was completely dominated by one particular idiotope (defined by plaque inhibition with the AB1-2 monoclonal antibody). On the other hand, the response of mice immunized with free antigen (PnC) was dominated to a lesser degree by the AB1-2 idiotope, and there was a great degree of variability in idiotope expression among individual mice. The results suggest that immunization with antigen/antibody complexes restricts the response to the expression of idiotopes that are present in the immune complex.