Quantitative changes in surface immunoglobulin expression in WEHI-231 lymphoma cells in relation to their proliferative rate

Abstract

Quantitative changes in surface immunoglobulin expression were studied in relation to the proliferative behavior of WEHI-231 cells. They undergo morphologic, biochemical and immunologic changes during the course of growth in culture. Changes in cell size and morphology, as well as DNA and RNA synthesis, resemble features of normal lymphocyte transformation. During log phase growth there was a more than 30-fold increase in cell number over a 4-day period in the absence of medium change. The average log phase population doubling time was 20 h. Plateau phase was achieved on day 5, and maintained through day 7. Image analysis studies of cytocentrifuged cells demonstrated increases in cell, and nuclear area that became apparent within 2 h of transplantation. Tritiated thymidine incorporation rose rapidly peaking on days 2 and 3, and then fell progressively to 35% of peak values on day 4. Tritiated uridine incorporation into RNA showed similar changes. Changes in S fraction, as determined by flow cytometry, paralleled the changes in tritiated thymidine incorporation. Cell surface IgM and kappa light-chain immunoglobulin were also measured by flow cytometry. Mean values were low initially, rose slowly, increased rapidly to peak values on days 3 and 4, and then fell progressively. Peak surface immunoglobulin levels were observed during the transition of cells from log phase to plateau phase growth, and coincided with the appearance of large numbers of small cells with low rates of DNA and RNA synthesis. Thus, maximum expression of surface Ig was associated with growth retardation, and not with early rapid growth phase. The maximal expression of surface immunoglobulin in small slowly proliferating cells may have important implications for immunotherapy with monoclonal antibodies alone.