The rate of dissociation between antibody and antigen determines the efficiency of antibody-mediated antigen presentation to T cells.
We analyzed the role of Ab affinity on Ab-mediated Ag uptake and presentation to T cells. Hen egg white lysozyme (HEL) was captured by bifunctional hybrid proteins (Fv-MalE) in which the variable fragment (Fv) of the anti-HEL mAb D1.3 was covalently linked to the Escherichia coli MalE protein. These complexes were targeted via two anti-MalE mAbs to an APC expressing a receptor for the Ab constant region. The combination of Fv-MalE and anti-MalE mAbs increased, specifically, HEL presentation. With this experimental system, we evaluated the impact of six different mutations, affecting the Fv-MalE complementarity determining regions, on the increase of HEL presentation by the corresponding hybrids. These mutations increase the dissociation rate constant (k(off)), and, thus, the dissociation constant of the HEL/Fv-MalE interaction, up to 650-fold, as compared with the wt Fv-MalE. Increasing the k(off) from 7 x 10(-4) s(-1) up to 300 x 10(-4) s(-1) did not interfere with the enhancement of HEL presentation. A mutant with a k(off) of 600 x 10(-4) s(-1) had a reduced enhancement ability, and mutants with k(off) higher than 5700 x 10(-4) s(-1) did not enhance HEL presentation at all. These results show that affinity determines the efficiency of Ab-mediated Ag presentation to T cells. One consequence is that affinity maturation in specific B lymphocytes can drastically enhance their ability to collaborate with T cells in an MHC-restricted way. This may contribute to the selection of high affinity B cell clones.
Guermonprez
P
P
Unité de Biologie des Régulations Immunitaires, Institut Pasteur, Paris, France.
England
P
P
Bedouelle
H
H
Leclerc
C
C
D018528:ATP-Binding Cassette Transporters; D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D000915:Antibody Affinity; D017951:Antigen Presentation / Q000276:immunology*; D000937:Antigen-Antibody Reactions; D001402:B-Lymphocytes / Q000276:immunology*; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology*; D002352:Carrier Proteins / Q000276:immunology; D004705:Endocytosis; D029968:Escherichia coli Proteins; D006207:Half-Life; D006825:Hybridomas / Q000276:immunology; D007128:Immunoglobulin Fragments / Q000276:immunology*; D007700:Kinetics; D008211:Lymphocyte Cooperation; D058619:Maltose-Binding Proteins; D051379:Mice; D008807:Mice, Inbred BALB C; D009004:Monosaccharide Transport Proteins; D009113:Muramidase / Q000276:immunology; D033902:Periplasmic Binding Proteins; D017452:Receptors, IgG / Q000276:immunology; D011993:Recombinant Fusion Proteins / Q000276:immunology; D013601:T-Lymphocytes / Q000276:immunology*
D018528:ATP-Binding Cassette Transporters; D000911:Antibodies, Monoclonal; D002352:Carrier Proteins; D029968:Escherichia coli Proteins; D007128:Immunoglobulin Fragments; C461619:MalE protein, E coli; D058619:Maltose-Binding Proteins; D009004:Monosaccharide Transport Proteins; D033902:Periplasmic Binding Proteins; D017452:Receptors, IgG; D011993:Recombinant Fusion Proteins; C055966:immunoglobulin Fv; C461599:maltose transport system, E coli; D009113:Muramidase