Characterization of immunologic and neuropathologic abnormalities in wasted mice

Mice bearing the autosomal recessive gene 'wasted' (wst/wst) have been reported to develop low or absent secretory immune responses, abnormal DNA repair mechanisms, and uncoordinated body movements. We have performed a detailed immunologic and neuropathologic investigation of the disease. Con A and LPS mitogenic responses of splenic lymphocytes as well as total serum Ig levels were equivalent in wst/wst and undiseased control littermates (wst/+ and +/+). Amounts of serum IgM, IgG2a, IgG2b, IgG3, and IgA, however, were reduced in wst/wst animals. FACS analyses of Ig⁺ and isotype-specific B cell populations revealed similar percentages of Ig⁺, μ⁺, γ⁺, and α⁺ cells in wst/wst and control mice. However, the percentage of 'very bright' Ig⁺ cells as well as 'very bright' heavy and light chain-specific B cell subpopulations was increased at least 10-fold in wst/wst B cells as compared with littermate controls. In addition, studies of Ig-specific mRNA accumulation in these animals revealed significant decreases in all isotypes except γ3 in spleens of wst/wst mice as compared with littermate controls. Neuropathologic studies in wst/wst mice showed prominent vacuolar degeneration of neurons within anterior horns of the spinal cord and the motor nuclei of the brain stem. No abnormalities were noted in Purkinje cells of the cerebellum nor within myelin sheaths. The abnormalities in the nervous system resembled human motor neuron disease rather than ataxia-telangiectasia as had been reported previously. The immunologic studies suggest that splenic B cells from wst/wst mice have a defect in the ability to 'switch' from membrane to secreted Ig. In adition, this mutation provides a mechanism to study regulatory interactions between the immune and nervous systems.