ATC Below SS

Abbreviations: Ag, antigen; VC, veiled cell; SS, subcapsular sinus of lymph node; ATC, antigen transport cells; pre FDC, FDC precursor; FDC, follicular dendritic cells; ICCOSOMES, immune complex coated bodies; Bm, B memory cells; Th, T helper cells; GC, germinal center; MEDULLA, lymph node medulla; BM, bone marrow; Pc, plasma cell; Ab, antibody.

This chart shows the current working model for the: 1. TRANSPORT of antigen from the subcapsular sinus of a lymph node to the lymphoid nodule follicle); 2. The PRESENTATION of antigen by the B cell to T helper cells; 3. The rout to germinal center formation and antibody production; 4. The FEEDBACK regulation of the anamnestic humoral immune response. The following is a brief interpretation of this model with reference to the chart. To see actual electron micrographs or data, click on the figures in the chart in succession. Please note that in most biological systems redundancies exist. Similarly, in antigen transport, other transport mechanism may exist which may operate in alternative ways. Another antigen transport mechanism is said to involve antigen transport by lymphocytes. Both this alternative antigen transport pathway and a transport mechanism involving lymphocytes are discussed in detail in the book (CTMI, 201) edited by Dr. Kosco-Vilbois. These are references by: Heinen et al., and by Szakal et al. (Press the REF buttons below.) The IMMUNOLOGICAL EVENTS in the alternative antigen transport pathway of immune mice are as follows: Sequence of events:: 1 min-24 hrs: Ag-Ab-C' com[lexes are transported from the subcapsular sinus (SS) to follicles where the FDC-network (or reticulum) develops; Day 1-3 Iccosome formation and dispersion of the immune complex coated beads or bodies (=somes) that are released by the FDC to transport the Ag to the B cells. Day 3-5 Endocytosis of iccosomes, Ag processing / presentation to Th cells by Bm cells; Day 3-10 Germinal center (GC) development. Day 3-7 Ab-forming precursors in GC migrate to lymph node medulla and bone marrow to produce Ab. Day 8-14 Ab production in medulla and bone marrow by plasma cells results in and the formation of a "ball of yarn"-like FDC dendrite convolutions for long-term retention of Ag. With time, decrease in circulating Ab leads to dissociation of Ag-Ab-C' complexes, the ball-like dendrite convolutions unravel, expose the retained Ag and the FDCs are activated for a new cycle of iccosome production. This cycling is thought to help maintain Ab levels and long-term immunity.