Lymphocyte-mediated activation of fibroblast proliferation and collagen production.

Among the many activities of antigen-triggered lymphocytes may be the control of fibroblast function. Thymus-dependent lymphocytes challenged with the specific antigen, dinitrophenylated ovalbumin or tetanus toxoid produced a nondialyzable factor(s) capable of causing dermal fibroblasts to undergo DNA synthesis. These fibroblasts, which exhibit basal proliferative levels in the absence of serum, responded to the lymphocyte factor with maximal thymidine incorporation at 48 to 72 hr. In addition, these activated fibroblasts significantly increased their production of protein of both the collagenous and noncollagenous types. This increase in protein synthesis preceded maximal proliferation. Thus, the fibroplasia consisting of increased numbers of fibroblasts and of increased collagen deposition associated with chronic inflammatory diseases may be the direct consequence of a specific antigenic challenge.