Clusters of perifollicular macrophages in normal murine skin: physiological degeneration of selected hair follicles by programmed organ deletion.
In back skin sections from adolescent C57BL/6 mice, regularly distributed, perifollicular inflammatory cell clusters (PICC) were found located around the distal noncycling portion of about 2% of all hair follicles examined. The PICC and the affected hair follicles were characterized during spontaneously developed or induced hair cycle stages, using antibodies against MHC Class II, F4/80, ER-MP23, NLDC 145, CD4, CD8, gammadeltaTCR, IL-1 receptor, and ICAM-1. PICC consisted predominantly of macrophages (MAC), accompanied by a few CD4+ cells, whereas gammadeltaTCR+ and CD8+ cells were absent. During anagen and catagen, some of the PICC+ hair follicles showed variable degenerative phenomena reminiscent of scarring alopecia: thickened basement membrane, ectopic MHC II expression, MAC infiltration into the follicle epithelium, and signs of keratinocyte apoptosis. Loss of distal outer root sheath keratinocytes was detected in 10% of PICC+ hair follicles (0.2% of all hair follicles). Because PICC were located in the vicinity of the bulge region, MAC-dependent damage to follicle stem cells might eventually lead to follicle degeneration. These perifollicular MAC clusters around selected hair follicles may indicate the existence of a physiological program of MAC-dependent controlled follicle degeneration by which damaged or malfunctioning follicles are removed by programmed organ deletion (POD).
Eichmüller
S
S
Department of Dermatology, Charite, Humboldt-Universitat zu Berlin, Berlin, Germany.
van der Veen
C
C
Moll
I
I
Hermes
B
B
Hofmann
U
U
Müller-Röver
S
S
Paus
R
R
D000818:Animals; D015496:CD4-Positive T-Lymphocytes / Q000166:cytology; D018414:CD8-Positive T-Lymphocytes / Q000166:cytology; D005260:Female; D005802:Genes, MHC Class II; D018859:Hair Follicle / Q000254:growth & development* / Q000276:immunology*; D006651:Histocytochemistry; D007150:Immunohistochemistry; D018799:Intercellular Adhesion Molecule-1 / Q000032:analysis; D008264:Macrophages / Q000166:cytology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D017472:Receptors, Interleukin-1 / Q000032:analysis; D053573:Receptors, Interleukin-1 Type I
D017472:Receptors, Interleukin-1; D053573:Receptors, Interleukin-1 Type I; D018799:Intercellular Adhesion Molecule-1