Establishment of CD4⁺ T Cell Clones Specific to Bovine β-Lactoglobulin and Analysis of Their Specificity

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Bovine β-lactoglobulin (β-LG) specific T cell clones, H1.1, 5G, 2.11G, and 6.11G were established from BALB/c mice and characterized. Surface phenotypes of clones were Thy1⁺, CD3⁺, CD4⁺, and CD8^-. All clones recognize β-LG in a I-A^d restricted manner. The T cell determinant region for H1.1 and 5G was identified as residues 42-56 of β-LG by proliferation assay with overlapping synthetic peptides covering the entire sequence of β-LG. The T cell determinant region for H1.1 was further delimited to residues 43-52 by using analog peptides. Previously we analyzed the T cell determinant regions of β-LG in BALB/c, C3H/He, and C57BL/6 mouse by polyclonal T cell proliferation assay and reported that residues 42-56 of β-LG constitute one of the major T cell determinants in BALB/c mice. Specificities of 2.11G and 6.11G were not identified by these synthetic peptides. Although reduction of disulfide bonds and CNBr cleavage of β-LG did not affect the antigen recognition by 2.11G and 6.11G, tryptic degradation of the protein caused a clearer decrease of response in 6.11G than in 2.11G.