INTERLEUKIN-2 AND INTERFERON-GAMMA RECRUIT DIFFERENT SUBSETS OF HUMAN PERIPHERAL-BLOOD MONOCYTES TO SECRETE INTERLEUKIN-1-BETA AND TUMOR NECROSIS FACTOR-ALPHA

  • 1 July 1989
    • journal article
    • research article
    • Vol. 77  (1) , 97-100
Abstract
Exposure of cultured human peripheral blood monocytes (PBMO) to interferon-gamma (IFN-.gamma.) enhances surface expression of the p55 subunit of the interleukin-2 receptor (IL-2R). Addition of IL-2 to IFN-.gamma. treated monocytes will stimulate subsequent release of interleukin-1 beta (IL-1.beta.) and tumour necrosis factor-alpha (TNF-.alpha.) due to enhancement of the transcriptional rate and stability of mRNA accumulation of both genes. The present study was aimed to investigate whether IFN-.gamma. and IL-2 will favour the release of IL-1.beta. and TNF-.alpha. by different subsets of human PBMO. To this end PBMO were separated into four fractions with densities ranging from 1.058 to 1.075 kg/l by means of discontinuous bovine serum albumin (BSA) gradient centrifugation. Following incubation of monocyte subsets in the presence or absence of IFN-.gamma. and IL-2 for a culture period of 24-48 h, cell-free culture supernatants were collected and assayed for IL-1.beta. and TNF-.alpha. activity by ELISA. Surface p55 IL-2R expression was detected by CD25 monoclonal antibody (MoAb) anti-IL-2R1 using immunofluorescence analysis. Although IL-2R1 expressing PBMO were equally distributed among the four fractions, IL-1.beta. secretion was found to reside mainly in the most dense fraction. The major TNF-.alpha. activity was detected, however, in supernantants obtained from cultures of PBMO with densities of 1.065-1.075 kg/l. These data demonstrate functional heterogeneity of subsets of human PBMO with respect to their capacity to produce distinct cytokines.