Human papillomavirus (HPV), primarily HPV 16 & 18, are strongly implicated in the development of squamous cell carcinoma of the penis. Three carcinoma in situ are associated with squamous cell carcinoma of the penis: 1) Bowen's disease which presents as leukoplakia on the shaft. Around 1/3 progress to squamous cell carcinoma
The innate immune system is the bodyâs first line of defense against infection by microorganisms such as viruses, bacteria, and parasites.
1 Innate (nonspecific) system responds quickly and consists of: 2  First line of defense - intact skin and mucosae prevent entry of microorganisms. 3  Second line of defense - antimicrobial proteins, phagocytes, and other cells.  Inhibit spread of invaders throughout the body.