Morphologic heterogeneity of human thymic nonlymphocytic cells.
The thymus is the central organ of the immune system. It is essential for the development and maintenance of normal immune system, especially cell-mediated immunity. From the morphological point of view, the thymus is divided into two main compartments, cortex and medulla. The thymic microenvironment consists of a network of reticular epithelial cells and other fixed and free cells. The microenvironment of thymus is very important for the selection and maturation of T cells. T cell differentiation occurs via T cell receptors. The major histocompatibility complex participates in interactions between T cells and thymic epithelial cells, in addition to interactions between T cells and dendritic cells, macrophages and myoid cells. The neuroendocrine system regulates early T cell differentiation by the transcription of neuroendocrine genes in the stromal network and expression of cognitive receptors by immature T cells. This work briefly summarizes morphological and ultrastructural characteristics of thymic epithelial cells, dendritic cells, macrophages and myoid cells. It is accompanied by the authors' own photomicrographs and electronmicrograph from a transmission electron microscope. All of these cells play a critical role in the proliferation, differentiation and selection of precursor cells in the T-cell lineage, but the precise mechanisms not well understudood.
Department of Histology and Embryology, Faculty of Medicine, Comenius University, Bratislava, Slovak Republic.
Ivan
I
Varga
Renata
R
Mikusova
Viera
V
Pospisilova
Paulina
P
Galfiova
Marian
M
Adamkov
Stefan
S
Polak
Stefan
S
Galbavy
D002454:Cell Differentiation; D048430:Cell Shape; D003713:Dendritic Cells / Q000166:cytology*; D004847:Epithelial Cells / Q000166:cytology*; D006801:Humans; D008264:Macrophages / Q000166:cytology*; D013601:T-Lymphocytes / Q000166:cytology; D013950:Thymus Gland / Q000166:cytology*