Quantitative light and electron microscopic changes in thymic reticular epithelial cells during Moloney-virus-induced lymphoma development

Estimation of the proliferation and maturation functions in a physiologically structured model of thymocyte development

The thymus provides a stable microenvironment for post-natal thymocyte development that is finely regulated by a complicated network of cytokines, chemokines, cell-cell contacts, etc., the dysregulations of which contribute to many immunologic diseases including malignant lymphomas. A physiologically structured model in the form of first order partial differential equation (PDE) was developed to simulate the whole process. The combined effects of the thymic microenvironment were conceptualized into two (proliferation and differentiation) fields to serve as kernels of the PDE. In this paper, a novel method is developed to estimate the maturity-time structures of the two fields based solely on cell population data that are experimentally viable. Numerical examples demonstrate the effectiveness of the present method in revealing the two-dimensional (maturity and time) landscapes of the thymic microenvironment.

Target cells and thymus microenvironment in the pathogenesis of thymic lymphomas in C57BL/Ka mice

In C57BL/Ka mice, the induction of thymic lymphomas either by inoculation of radiation leukemia virus (RadLV) or by a split dose irradiation requires complex cellular events: Target cells are found among the population of thymic subcapsular blast cells, or, alternatively, of marrow or spleen prothymocytes; Progression of target cells to lymphoma growth requires a multi-step process, which occurs only within thymic microenvironment; Target cells are rapidly induced as "preleukemic" cells; After inoculation of RadLV, the initial events occur when target cells are in close association with cells of a specialized component of thymic epithelium, i.e., the so-called "nurse cells"; The leukemogenic agents induce damages to the thymic microenvironment itself; Lymphoma prevention by marrow grafting after irradiation results from mechanisms still unknown which inhibit the progression of "preleukemic" cells to neoplastic growth.