HISTAMINE-RELEASING ACTIVITY (HRA) .1. PRODUCTION BY MITOGEN-STIMULATED OR ANTIGEN-STIMULATED HUMAN MONONUCLEAR-CELLS

Abstract

Supernatants from 1-2 day cultures of human mononuclear cells induced the release of histamine from basophils. Generation of this histamine-releasing activity (HRA) was stimulated by addition of concanavalin A to the cell cultures. Mononuclear cells were cultured with SKSD [streptokinase-streptodornase] and Candida albicans antigens [Ag]. Stimulation of HRA production by these Ag was correlated with positive delayed skin reactions. Serial dilutions of supernatants assayed for HRA provided a semiquantitative determination of the level of HRA in mitogen- or Ag-stimulated samples. Ag increased HRA production when added during the 1st or 2nd day of culture. Generation of HRA probably requires active protein synthesis, since puromycin was inhibitory and pre-formed HRA could not be recovered from lysed cells. HRA was detected in supernatants after 4 h and the effects of Ag stimulation were apparent after 8 h of culture. The rate of HRA synthesis diminished after 18 h of culture. Replacement of supernatants with fresh culture medium allowed continued synthesis of substantial quantities of HRA during the 2nd day of culture. A linear correlation was observed between the amount of HRA produced and the mononuclear cell concentration. Lymphocytes and basophils may interact via a soluble mediator.