HPV infects which cells first:
**Core Concept**
Human Papillomavirus (HPV) primarily infects the basal cells of the epithelial layer. The virus binds to the integrin α6β4 receptor on the surface of these cells, initiating the infection process.
**Why the Correct Answer is Right**
HPV uses its L2 protein to bind to the integrin α6β4 receptor on the surface of basal cells. This interaction allows the virus to gain entry into the cell and initiate the replication process. The virus then integrates into the host genome, leading to the expression of viral oncogenes that contribute to the development of cervical cancer and other HPV-related diseases.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because HPV does not primarily infect keratinocytes, which are a type of epithelial cell found in the outer layer of the skin and mucous membranes.
**Option B:** This option is incorrect because HPV does not initially infect immune cells, such as T cells or macrophages.
**Option C:** This option is incorrect because HPV does not primarily infect stem cells, which are a type of cell that has the ability to differentiate into multiple cell types.
**Clinical Pearl / High-Yield Fact**
HPV infection is a major risk factor for cervical cancer, and the virus is responsible for approximately 99% of all cervical cancer cases. The HPV vaccine is effective in preventing infection with the most common high-risk HPV types, such as HPV 16 and 18.
**Correct Answer:** C. Basal cells of the epithelial layer.