Innate and acquired immunity in the human penile urethra

Abstract

In men, the penile urethra is a primary infection site for sexually transmitted pathogens. Research on the immunology of this mucosal site has been limited in part due to sampling challenges, but available evidence indicates that the urethra contains a rich contingent of immunological mediators that can mount vigorous innate and adaptive immune responses against infectious organisms. Further research is needed to define approaches to stimulate immunity at this mucosal site to prevent the transmission of HIV-1 and other sexually transmitted pathogens.

Figure 1

Fig. 1. a) Diagram of human male genital tract (From: Gray H. Anatomy of the Human Body. Philadelphia: Lea and Febiger, 1918), b) Transition from the fossa navicularis on the right (stratified squamous epithelium) to the penile urethra (pseudostratified columnar epithelium) on the left, c) glands of Littre (arrows)

Figure 2

Mediators of innate immunity in the penile urethral mucosa. a) Expression of TLR9 by urethral epithelium, b) Granulocytes present in urethral epithelium, c) expression of TLR1 by urethral granulocytes, d) Expression of interferon-α in urethral epithelium, e) lysozyme detected in the glands of Littre, f) Lactoferrin detected in urethral epithelium, g) SLPI in urethral epithelium.

Figure 3

Mediators of adaptive immunity in the penile urethral mucosa. a) CD1a+ dendritic cells in epithelium of the meatus, b) macrophages present in the epithelium of the penile urethra, c) CD8+ lymphocytes in the urethral epithelium, d) CD4+ lymphocytes in the lamina propria of the urethral mucosa, e) CD103+ lymphocytes in the urethral mucosa, f) TIA+ lymphocytes in the urethral epithelium and lamina propria.

Figure 4

Mediators of humoral immunity in the penile urethral mucosa. a) IgA+ plasma cells, b) IgM+ plasma cells, c) Plasma cells expressing J-chain, d) Urethral epithelium expressing the polymeric Ig Receptor.