The calcium-binding protein calretinin is a marker of the companion cell layer of the human hair follicle.
BACKGROUND
Ultrastructural studies of the hair follicle show that the outer root sheath (ORS) does not consist of a homogeneous cell population. The innermost cell layer of the ORS, also called the companion layer, is a single cell layer closely associated with the Henle layer of the inner root sheath.


OBJECTIVE
To describe the immunohistochemical expression of calretinin, a calcium-binding protein, in the human hair follicle.


METHODS
Immunohistochemical studies using two different antisera to calretinin were performed in paraffin-embedded and in frozen scalp specimens using standard techniques.


RESULTS
Calretinin immunostaining was consistently and specifically found in the companion cell layer of hair follicles.


CONCLUSIONS
These findings provide further evidence to support the notion that the companion layer is not only morphologically, but also immunohistochemically, different from the other cells of the ORS.
Poblet
E
E
Dermatology of Pathology, Hospital General Universitario de Albacete and Universidad de Castilla La Mancha, Spain.
Jimenez
F
F
de Cabo
C
C
Prieto-Martin
A
A
Sánchez-Prieto
R
R
D000368:Aged; D015415:Biomarkers / Q000032:analysis; D064032:Calbindin 2; D005260:Female; D005455:Fluorescent Antibody Technique; D019085:Fluorescent Antibody Technique, Direct; D018859:Hair Follicle / Q000737:chemistry* / Q000648:ultrastructure; D006801:Humans; D008297:Male; D008875:Middle Aged; D064030:S100 Calcium Binding Protein G / Q000032:analysis*; D012535:Scalp
D015415:Biomarkers; C576764:CALB2 protein, human; D064032:Calbindin 2; D064030:S100 Calcium Binding Protein G