    Sentence 1: Wat is'the most’ tonirhai{ cause ef:  tinniunodeficieney th developing naticins?    Sentence 2: The ability ofthe immurie’ sistem to  respond to “pathoperjs is diniinished inj both: the  oung and the-elderlg-with iminune pesponsés  ginhing to dettine at atounid 50 years of ape  due to'imniutiosohegcenie,: 50° °F"                                