Rare spelling of 抗原 (“antigen”).

cause, bring about / pull up to a standing position

a certain one, particular one, specific one

specify, identify, determine

fight against / meet head on / contravene / to disagree with

chemical reaction / reaction, response / feedback

to react chemically / to respond, to react / be responsive, be sensitive

cause, origin / basis, foundation / cost / (finance) capital / principal

(immunology) immunity / habituation

former, erstwhile