T Cell Activation Sequence
Step 1 of 6
T Helper CD4+ CTL CD8+ MHC II Cytokines MHC I Perforin APOPTOSIS Clonal expansion APC presents antigen on MHC II
Step 1 — Antigen Presentation to T Helper Cell
A dendritic cell (antigen-presenting cell) engulfs a pathogen, digests it, and displays antigen fragments on MHC class II molecules.
Only professional antigen-presenting cells (dendritic cells, macrophages, B cells) express MHC class II. The T helper cell TCR binds to this complex.
Which molecule presents antigen to the T helper cell?
Task: Trace the full T cell activation pathway from antigen presentation to infected-cell destruction. Answer each question to advance.
Tip: T helpers coordinate via cytokines; CTLs kill via perforin and granzymes. Both need activation signals. Press R to restart.