| Date | May 2009 | Marks available | 1 | Reference code | 09M.1.HL.TZ2.15 |
| Level | Higher level | Paper | Paper 1 | Time zone | Time zone 2 |
| Command term | Question number | 15 | Adapted from | N/A |
Question
When a pathogen is ingested by a phagocyte, which event occurs first?
A. T-cell activation
B. Memory cell proliferation
C. Antigen presentation by the phagocyte
D. B-cell activation
Markscheme
C
Examiners report
This question also had a high discrimination index, where the good candidates knew that antigen presentation by the phagocytes is the first event after a pathogen is ingested by a phagocyte, although the word phagocyte in the answer possibly gave the answer away.
