Teacher you are right, punctuation in the text wasn´t (isn´t) that good.

     Plus, our learner did not do any favour by ommiting parts of paragraph, it seems like it was just cut from a Google´s search. The learner had not even the grace of entering the article...   It´s no wonder Google Translator itself couldn´t do its job properly.

http://www.jleukbio.org/content/71/1/16.full.pdf

   Our understanding of the effect of nutrients on immune function has been refined as the field of immunology has grown from a descriptive science to one in which diverse immune phenomena can be tied together coherently and explained in quite precise structural and biochemical terms.

    In other words, our mass of knowledge about the nutrients role into immunology studies has improved and turned from (a mere...! or less accurate) descriptive science into a broader one, and way more precise.