Dominant role of monocytes in control of tissue function and aging

We propose that monocyte-derived cells regulate expression of epitopes of specific tissue cells, and in that way control recognition of tissue cells by autoreactive T lymphocytes and autoantibodies. Such T cells and antibodies are suggested to participate in stimulation of tissue cell differentiation. This may ultimately result in the aging and degeneration of tissue cells. By the end of their adaptation in early ontogeny, the monocyte-derived cells are supposed to encounter the most differentiated tissue cells in a tissue specific manner, and then prevent tissue cells to differentiate beyond the encoded state. Retardation or acceleration of certain tissue differentiation during adaptation results in a rigid and permanent alteration of this tissue function. The ability of monocytes to preserve tissue cells in the functional state declines with age, and this is accompanied by functional decline of various tissues within the body, and an increased incidence of degenerative diseases. (C) 2000 Harcourt Publishers Ltd.