Abstract
Actions of β-carotene isomers including all-trans-, 9-cis, and 13-cis-β-carotene and a β-carotene isomer mixture extracted from alga were examined in regard to T-helper (Th) cell function for antibody (Ab) production. β-carotene isomers did not significantly enhance in vitro Ab production by murine spleen cells, which may be partly due to the paucity of antigen (Ag)-specific Th cells. We thus replaced Th cells in spleen cell suspensions with Ag-specific Th clones in order to increase the frequency of Ag-specific Th cells. Then β-carotene isomers' effects on in vitro Ab production were reassessed. In this system, the enhancing actions of β-carotene isomers on Ab production were more evident compared to controls: (1) when cells were stimulated with suboptimal doses of Ag, and (2) when a type-2 T-helper (Th2) cell clone was used. The effects of all-trans-and 9-cis-β-carotene did not differ significantly, but the effects of 13-cis-β-carotene on Th clones was less than those exhibited by other β-carotene isomers. Ag-potentiated cytokine production by Th clones was not significantly altered by β-carotene isomers. In summary, our results suggest that β-carotene can modulate Th cell functions for Ab production in the presence of a suboptimal dose of Ag.
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