The human hair follicle: glycoprotein-related antigenic profile of distinct keratinocyte populations in vivo and their alterations in vitro.

The cell surface expression of three glycoprotein antigens, as defined by the monoclonal antibodies BT 15, T 43, and MH 99, was investigated in follicular keratinocyte populations in vivo. In addition, the regulation of glycoprotein synthesis was studied in follicular and interfollicular keratinocytes cultured in vitro. The BT 15 antigen was strongly expressed in the inner root sheath and the area above Auber's line of the hair bulb, whereas the T43 antigen was mainly seen in the outer root sheath. Selectively high expression of the MH 99 antigen was found only in outgrowing germ buds of early anagen follicles. Radioimmunoprecipitation revealed strong signals with BT 15 in freshly prepared follicular keratinocytes, two to three times stronger than those in interfollicular keratinocytes, but the signals clearly decreased by 80% under continuing culture conditions. The T 43 antigen was found by FACS analysis and radioimmunoprecipitation in initially low amounts in both populations, but the signals increased dramatically (up to 50 times) in long-term cultures and in subcultures. The MH 99 antigen was also initially present only in low amounts, in interfollicular rather than in follicular keratinocytes, but its expression increased up to 15-fold with continuing culture and any differences between the two populations disappeared. Our investigation revealed that at least three populations of hair follicle keratinocytes are characterized by different surface glycoprotein antigens, clearly related to their state of differentiation and proliferation.(ABSTRACT TRUNCATED AT 250 WORDS)