Macrophage uptake and retention of radiolabeled glycopeptidolipid antigens associated with the superficial L1 layer of Mycobacterium intracellulare serovar 20

Abstract

Glycopeptidolipid (GPL) antigens which are associated with the superficial L1 layer of Mycobacterium intracellulare serovar 20 were labeled with radioisotopes by means of internal labeling techniques and used in macrophage uptake and retention studies. The use of tritiated alanine and phenylalanine allowed the incorporation of label into the GPL invariant fatty acyl peptide core, which is common to all members of the Mycobacterium avium-M. intracellulare complex. Radiolabeled GPL antigens were then purified by a one-step column chromatographic procedure and subsequently used to determine the maximum uptake and retention in peritoneal macrophages isolated from C57BL/6 and CBA/J mice. Maximum uptake for peritoneal macrophages from both strains of mice occurred at a concentration between 200 and 250 micrograms of antigen per ml of medium when 3.4 X 10(5) cells were pulsed. Timed experiments demonstrated that approximately 20% of the antigens remained associated with the macrophages up to 4 days after a pulse of 200 micrograms of GPL, and examination of chloroform-extractable components from both macrophages and spent medium revealed that 98% or more of the radioactivity corresponded to intact GPL components. The ability of the GPL antigens to become associated with macrophages is demonstrated by these results, which strongly suggest that these potentially important mycobacterial antigens are inert to degradation by those cells.