Histamine-induced suppressor macrophage inhibits fibroblast growth and wound healing

To determine whether there is histamine-induced suppressor activity in macrophage-related functions other than in immunity, extracts and media from a macrophage cell line, RAW 264, were tested for suppressor effect on fibroplasia. The procedure consisted of priming confluent RAW 264 cells in culture with media or cellular extracts of washed mastocytes (P-815). The inoculum was removed from the RAW 264 cells by rinsing with fresh medium 24 hours later, and then with medium replacement and 3 more days of culture. The culture media or extracts of washed RAW 264 cells were tested for suppressor activity. The primed RAW 264 cells were lysed by 4 freeze-thaw cycles and cleared by centrifugation, and the resulting supernatant was tested on fibroblast (3T3) cell growth and wound healing in mice and for suppressor activity on T cells. Replication of 3T3 cells, as quantitated by uptake of [3H]thymidine, was reduced 75% when "suppressor" material from RAW 264 cells was added to 3T3 cultures and not when media or extracts of unprimed RAW 264 cells were added. Tensiometric measurements of wound breaking strength (full-thickness incised wounds) were reduced 31% by day 4 and 47% by postsurgical day 7 when "suppressor" RAW 264 extracts were instilled into wounds. Leukocyte cultures stimulated with phytohemagglutinin had a reduced uptake of [3H]thymidine (suppressed 90% to 95%) when exposed to primed RAW 264 extracts, whereas kidney cell culture lines were unaffected. The data obtained indicated that mastocyte (histamine)-induced suppressor factors are present for fibroblast activity as well as T-cell function.