Sentence:  For example , the marked susceptibility of the monkey to respiratory <WSD>infection</WSD> might be related to its delicate , long alveolar ducts and short , large bronchioles situated within a parenchyma entirely lacking in protective supportive tissue barriers such as those found in types 1 , and 3 , . 
Meaning of the word marked with <WSD> tags:  the pathological state resulting from the invasion of the body by pathogenic microorganisms