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Expression of decay-accelerating factor (CD55) of the complement system on human spermatozoa
F Cervoni1, T J Oglesby, P Fénichel
1Institut National de la Santé et de la Recherche Médicale, Faculté de Médecine, Nice, France.
Journal of Immunology (Baltimore, Md. : 1950)
|July 15, 1993
Summary
Human sperm express decay-accelerating factor (DAF, CD55) on their heads, which protects them from complement-mediated damage. This finding suggests a role for DAF in sperm immune protection within the female reproductive tract.
Area of Science:
- Immunology
- Reproductive Biology
- Complement System
Background:
- Decay-accelerating factor (DAF, CD55) is a regulatory protein of the complement cascade.
- DAF is typically a glycolipid-anchored protein found on various human tissues.
- The complement system plays a role in immune responses within the female genital tract.
Purpose of the Study:
- To investigate the expression and function of DAF on human spermatozoa.
- To determine the molecular characteristics and localization of sperm DAF.
- To assess the potential role of sperm DAF in protecting spermatozoa from complement-mediated lysis.
Main Methods:
- Immunofluorescence microscopy to localize DAF on spermatozoa.
- Immunoprecipitation and Western blotting to analyze DAF protein.
- Carbohydrate analysis to characterize DAF glycosylation.
- Functional assays using sheep erythrocytes to assess complement inhibition.
Main Results:
- DAF is localized to the acrosomal region of human sperm heads.
- Sperm DAF is a 44- to 54-kDa protein with nonsialated N- and O-linked sugars, differing in mass from DAF on other tissues.
- Sperm DAF possesses a glycolipid anchor and can inhibit complement-mediated lysis of erythrocytes.
- Monoclonal antibodies blocking DAF function reversed its inhibitory effect.
Conclusions:
- Human spermatozoa express a unique form of DAF (CD55) with a glycolipid anchor.
- Sperm DAF likely protects acrosome-reacted spermatozoa from complement attack in the female genital tract.
- DAF may function with other complement regulators, like membrane cofactor protein, to modulate complement activation.