The human thymus. I. Partial characterization of nonlymphoid cells.

Human thymus was disrupted by mechanical and enzymatic techniques yielding tissue fragments and single-cell suspensions. Cell types and their distribution were determined before and after density separation. Single-cell suspensions produced by both separation procedures yielded comparable percentages of lymphoid and monocytic cells, whereas only the enzyme-treated tissue yielded epithelial cells. Less than 1% of all monocytic cells were mature. Monolayer cultures were established from fragments as well as unfractionated cells and gradient fractions. Analysis of these cultures showed that: (1) gradient separation of mechanically-prepared cell suspensions produced cultures enriched for macrophages, while epithelial cell cultures could be produced from fractionated enzyme treated tissue; (2) spindle-shaped cells may be fibroblasts or epithelial cells; (3) explant cultures have a growth pattern characteristic of other epithelial cells in vitro; (4) macrophages constitute a definite population of explanted cells and their percentages increase with time in culture; (5) macromolecular synthesis by epithelial cells in culture may be donor age dependent. Nonlymphoid cells of the human thymus can be identified by a variety of separation techniques and after monolayer culture. Characteristics of these cells are defined which may affect cell-cell interaction studies of the thymus.