Final answer:
Interleukins are a subclass of cytokines released by CD4+ helper T cells that can trigger MMP activation in the cell-mediated immune response.
Step-by-step explanation:
The question asks which cytokine triggers the activation of matrix metalloproteinases (MMPs) in the cell-mediated immune response, specifically referring to CD immune response, which often involves CD4+ helper T cells. The CD4+ helper T cells become activated upon binding to an MHC II-antigen complex on an antigen-presenting cell (APC), leading to the release of various cytokines. One important group of cytokines in the regulation of MMP activation is the interleukins, especially those involved in pro-inflammatory responses. Although the question does not specify which MMP or the context, typically in immune responses involving CD4+ T cells, a range of interleukins can be implicated in upregulating MMPs to modulate the extracellular matrix during an immune response.