A novel in vivo follicular dendritic cell-dependent iccosome-mediated mechanism for delivery of antigen to antigen-processing cells.

摘要: Recent scanning electron microscopic studies on isolated follicular dendritic cells (FDC) showed that dendrites of certain FDC were "beaded," i.e., consisting a series interconnected immune complex coated bodies (termed "iccosomes," measuring 0.3 to 0.7 micron diameter). In vitro these iccosomes detach from one another with ease. The major objectives herein establish whether structures can be detected in sections and serve disseminate antigen vivo. Beginning at day 1, the time point used for isolating beaded FDC, popliteal lymph nodes C3H mice studied light transmission microscopy 2 wk (i.e., days 3, 5, 8, 14) after hind footpad injection histochemically detectable antigen, horseradish peroxidase (HRP). Iccosomes (0.25 0.38 diameter), contoured by (PO)-positive coat HRP-anti-HRP complexes, first 1 adjacent cell FDC. Within their limiting membrane they contained flocculent material was PO positive. At 3 microscopy, germinal centers seen enlarged antigen-retaining reticulum, composed antigen-bearing appeared diffuse. This coincided visualization dispersed state among lymphocytes. attached surface lymphocytes via PO-positive complexes surrounded microvillous processes cells. Germinal center tingible body macrophages both responded contact endocytosis. Antigen-containing macrophage most conspicuous when majority endocytosed HRP secondary lysosome-like granules associated Golgi apparatus. number markedly reduced 5. controls injected HSA, PO-negative PO-negative. presence types confirmed through use gold-conjugated (goat IgG). Simultaneous immunoperoxidase labeling same tissues anti-Ia gold conjugate containing B Ia+. Antigen-positive greatly numbers 14, suggesting intracellular fragmentation antigen.(ABSTRACT TRUNCATED AT 400 WORDS)