Definition: In this task you will be given a text passage from a trivia quiz. You should choose the category this question belongs to from these categories: History, Science, Social Science, Fine Arts, Literature. You can only choose one category, so if in doubt, please choose the closest match.
Input: A chaperone unique to these cells removes CLIP from the invariant chain protein. An ABC-class transporter unique to these cells is TAP, which transports peptides to the ER's peptide-loading complex. The avidity model explains the differential development of these cells. By suppressing NF-AT transcription factors, cyclosporine prevents the growth of these cells. These cells are regulated by both positive and negative selection, and they undergo somatic recombination but not somatic hypermutation. These cells present the major histocompatibility complex. One class of these cells has the CD8 glycoprotein on its surface and secretes perforin and granzymes. For 10 points, name these lymphocytes which come in "helper" and "cytotoxic" forms and mature in the thymus.
Output:
Science