TY - JOUR
T1 - The dual function of the splenic marginal zone
T2 - essential for initiation of anti-TI-2 responses but also vital in the general first-line defense against blood-borne antigens
AU - Zandvoort, A
AU - Timens, W
PY - 2002/10
Y1 - 2002/10
N2 - The splenic marginal zone (S-MZ) is especially well equipped for rapid humoral responses and is unique in its ability to initiate an immune response to encapsulated bacteria (T-cell independent type 2 (TI-2) antigens). Because of the rapid spreading through the blood, infections with blood-borne bacteria form a major health risk. To cope with blood-borne antigens, a system is needed that can respond rapidly to a great diversity of organisms. Because of a number of unique features, S-MZ B cells can respond rapid and efficient to all sorts of blood-borne antigens. These unique features include a low blood flow microenvironment, low threshold for activation, high expression of complement receptor 2 (CR2, CD21) and multireactivity.Because of the unique high expression of CD21 in a low flow compartment, S-MZ B cells can bind and respond to TI-2 antigens even with relatively low-avid B cell receptors. Although TI-2 antigens are in general poorly opsonized by classic opsonins, a particular characteristic of these antigens is their ability to bind very rapidly to complement fragment C3d without the necessity of previous immunoglobulin binding. TI-2 primed S-MZ B cells, already by first passage through the germinal centre, will meet antigen-C3d complexes bound to follicular dendritic cells, allowing unique immediate isotype switching. This explains that the primary humoral response to TI-2 antigens is unique in its characterization by a rapid increase in IgM concurrent with IgG antibody levels.
AB - The splenic marginal zone (S-MZ) is especially well equipped for rapid humoral responses and is unique in its ability to initiate an immune response to encapsulated bacteria (T-cell independent type 2 (TI-2) antigens). Because of the rapid spreading through the blood, infections with blood-borne bacteria form a major health risk. To cope with blood-borne antigens, a system is needed that can respond rapidly to a great diversity of organisms. Because of a number of unique features, S-MZ B cells can respond rapid and efficient to all sorts of blood-borne antigens. These unique features include a low blood flow microenvironment, low threshold for activation, high expression of complement receptor 2 (CR2, CD21) and multireactivity.Because of the unique high expression of CD21 in a low flow compartment, S-MZ B cells can bind and respond to TI-2 antigens even with relatively low-avid B cell receptors. Although TI-2 antigens are in general poorly opsonized by classic opsonins, a particular characteristic of these antigens is their ability to bind very rapidly to complement fragment C3d without the necessity of previous immunoglobulin binding. TI-2 primed S-MZ B cells, already by first passage through the germinal centre, will meet antigen-C3d complexes bound to follicular dendritic cells, allowing unique immediate isotype switching. This explains that the primary humoral response to TI-2 antigens is unique in its characterization by a rapid increase in IgM concurrent with IgG antibody levels.
KW - splenic marginal zone
KW - B cells
KW - memory
KW - T-cell independent type 2 antigens
KW - pneumococcal polysaccharides
KW - MEMORY B-CELLS
KW - INDEPENDENT TYPE-2 ANTIGENS
KW - HUMORAL IMMUNE-RESPONSE
KW - VARIABLE REGION GENES
KW - HUMAN LYMPHOCYTES-B
KW - PNEUMOCOCCAL POLYSACCHARIDES
KW - ACQUIRED-IMMUNITY
KW - SIGNAL-TRANSDUCTION
KW - ANTIBODY-RESPONSES
KW - TI-2 ANTIGENS
M3 - Review article
SN - 0009-9104
VL - 130
SP - 4
EP - 11
JO - Clinical and Experimental Immunology
JF - Clinical and Experimental Immunology
IS - 1
ER -