Modulation of the T cell response to beta-lactoglobulin by conjugation with carboxymethyl dextran.
We have previously prepared beta-lactoglobulin (beta-LG)-carboxymethyl dextran (CMD) conjugates with water-soluble carbodiimide and achieved reduced immunogenicity of beta-LG. In the present study, to elucidate the mechanism for the reduced immunogenicity of beta-LG, we investigated changes in the T cell response to beta-LG after conjugation with CMDs differing in molecular weight (about 40 and 162 kDa). Lymph node cells from BALB/c, C3H/He, and C57BL/6 mice that had been immunized with beta-LG or the conjugates were stimulated with beta-LG, and the in vivo T cell response was then evaluated by BrdU (5-bromo-2'-deoxyuridine) ELISA as the ex vivo proliferative response. T cells from the conjugate-immunized mice showed a lower proliferative response than those from the beta-LG-immunized mice. T cell epitope scanning, using synthesized peptides, showed that the T cell epitope profiles of the conjugates were similar to those of beta-LG, whereas the proliferative response to each epitope was reduced. These results indicate that the lower in vivo T cell response with the conjugates was not due to induction of conjugate-specific T cells, but due to a decrease in the number of beta-LG-specific T cells. After the lymph node cells from beta-LG-immunized mice had been stimulated with beta-LG or the conjugates, the efficiency of the antigen presentation of the conjugate to beta-LG-specific T cells was evaluated by BrdU ELISA as the in vitro proliferative response. The antigen presentation of beta-LG to the T cells was reduced by conjugation with CMD. In addition, conjugation with CMD enhanced the resistance of beta-LG to cathepsin B and cathepsin D, which suggest that conjugation with CMD inhibited the degradation of beta-LG by proteases in APC and led to suppression of the generation of antigenic peptides including T cell epitopes from beta-LG. It is therefore considered that the suppressive effect on the generation of T cell epitopes reduced the antigen presentation of the conjugates and that this reduction led to a decrease in the number of beta-LG-specific T cells in vivo. As a result, the decreased help to B cells by T cells would have reduced the antibody response to beta-LG. We conclude that suppression of the generation of T cell epitopes by conjugation with CMD is important to the mechanism for the reduced immunogenicity of beta-LG.
Kobayashi
Kazuo
K
Department of Applied Biological Science, Faculty of Agriculture, Tokyo University of Agriculture and Technology, Tokyo, Japan.
Yoshida
Tadashi
T
Takahashi
Koji
K
Hattori
Makoto
M
D000276:Adjuvants, Immunologic / Q000737:chemistry* / Q000494:pharmacology; D000818:Animals; D017951:Antigen Presentation; D003911:Dextrans / Q000737:chemistry*; D010450:Endopeptidases / Q000378:metabolism; D018604:Epitope Mapping; D007114:Immunization; D007782:Lactoglobulins / Q000737:chemistry* / Q000276:immunology*; D008198:Lymph Nodes / Q000166:cytology / Q000276:immunology; D008213:Lymphocyte Activation; D051379:Mice; D008815:Mice, Inbred Strains; D008970:Molecular Weight; D013601:T-Lymphocytes / Q000276:immunology*
D000276:Adjuvants, Immunologic; D003911:Dextrans; D007782:Lactoglobulins; C014392:carboxymethyl dextran; D010450:Endopeptidases