Identification and purification of a receptor on macrophages for the dengue virus-induced suppressor cytokine

SUMMARY Dengue type 2 virus (DV)-induced suppressor cylokine (SF) binds to macrophages to transmit the suppressor signal to recruit the second subpopulation of suppressor T cells. The present study was undertaken to identify and purify the receptor for SF(SF-R) on macrophages. The binding of 125I-SF to macrophages was saturable and reversible. Scatchard analysis showed the presence of both high (54 000/cell) and low (178 × 106/cell) affinity receptor sites. The binding of 125I-SF to macrophages was inhibited by pretreatment of macrophages with anti-SF antiseruin but not by a heterologous antiserum. Normal mouse peritoneal macrophage membrane was solubilized with Triton-X-100 and the components separated by low pressure liquid chromatography (LPLC) to purify SF-R. The presence of SF binding moiety (SF-R) was screened at each step of purification. The purified SF-R resolved into two bands of 45–50 kD mol. wt on SDS-PAGE. 125I-SF + SF-R complex run on SDS-PAGE showed a single band at about 55–60 kD mol. wt by autoradiography. Anti-SF-R anti serum reacted with SF-R in a Western blot test; the reaction was abolished by pretreatment of the blots with proteinase K, but not by pretreatment with periodic acid. SF-R was composed of two polypeptide chains (α and β) which were obtained in pure form by high performance liquid chromatography (HPLC) of dithiothreitol- and iodoacetamide-treated SF-R. Only the β chain bound SF.