transitional cell


tran·si·tion·al cell

any cell thought to represent a phase of development from one form to another.

T cell

Cardiology
A specialised myocyte found in clusters in the sinus node, which is intermediate in size, structure, and organisation between P cells and normal atrial myocytes, and connect swith either of these cells; perinodal T cells surround the sinus tract and are thought to “bundle” impulses leaving the sinus node and to filter premature ectopic atrial impulses.
Immunology
A thymus-derived white cell responsible for cell-mediated immunity and immunoregulation which is the most complex cell of the immune system, given:
(1) The diversity of T-cell types, including T cells with activator, cytotoxic, delayed hypersensitivity and suppressor activities;
(2) The wide range of cytokines, growth factors and immune modulators produced by activated T cells;
(3) The complexity of T-cell interaction with exogenous and endogenous antigens (e.g., mediation of delayed hypersensitivity, graft-versus-host disease);
(4) The complexity of T-cell maturation in the thymus.
50 to 70% of circulating WBCs are granulocytes (neutrophils); the rest are lymphocytes, of which T cells (defined as having “pan T cell” markers), CD2 and CD7 and other T-cell markers (e.g., CD1, CD3, and CD5) comprise 70 to 85%; B cells comprise 15 to 30%.

transitional cell

The stretchable epithelial cells that compose the transitional epithelium (uroepithelium), which lines most of the urinary tract. Transitional cells are strongly interconnected. They are cuboidal when not under pressure, and they become flattened and squamous when stretched. Transitional epithelia are 4-6 cells thick, and the top transitional cells -- those on the lumenal surface -- fuse to become larger and polyploid. See also: cell