SLO (Secondary Lymphoid tissue)
share common B and T cell areas
they share common B and T cell areas. B cells are present in B cell follicles close to T cell zones, thus allowing the encounter of T and B cells activated by the same antigen
Cortex
- an outer region composed of B cell follicles
- an inner region, the paracortex, composed of T lymphocytes
入：高内皮微静脉；出：efferent lymphatics（未激活淋巴细胞）
B and T cells enter the node from the blood by crossing the specialized high endothelial venules located in the paracortex. If they are not activated by an antigen, they return to the circulation via the efferent lymphatics and the thoracic duct.
Initiation of the Immune Response in Lymph Nodes
- CD163+ macrophage -> B cell follicles
Soluble antigens
- enter small channel called conduits -> B cell follicles
immune complexes
retained by follicular dendritic cells (FDCs) by CR1/2 (CD35) or their Fc receptor, FcγRIIB (CD32)
- CR1/2 (CD35)
- FcγRIIB (CD32)
FDCs recycle unprocessed antigens through a non-degradative endocytic pathway that allows them to retain and reexpress them over a long period of time.
Subcapsular sinus macrophages can also transfer immune complexes to noncognate B cells, which then transfer them to FDCs. 4 SIGN-R1+ dendritic cells (DCs) can also carry antigens to B cell follicles.