Complement regulatory proteins on the sperm surface: relevance to sperm motility.
OBJECTIVE
To determine whether complement regulatory proteins are present on human spermatozoa and whether antibodies to these proteins adversely affect sperm motility.


METHODS
Human sperm membrane proteins were solubilized and subjected to polyacrylamide gel electrophoresis followed by Western blot analysis against antibodies to complement component 1 inhibitor (C1-INH), decay-activating factor (DAF; CD55), membrane cofactor protein (MCP; CD46), and homologous restriction factor (HRF; CD59). Spermatozoa, obtained by a swim-up technique, were incubated in medium (control 1) and medium supplemented with antibodies to human albumin (control 2) and antibodies to these complement regulatory proteins. We used a computerized sperm motion analysis to determine the effect of these antibodies on sperm motion characteristics.


RESULTS
Complement regulatory proteins such as C1-INH, CD55, CD46, and CD59 were found in the sperm extracts as shown by Western blot analysis. The heat-treated (56 degrees C, 30 min) IgG fraction of antibodies to these proteins significantly reduced sperm motility in general and other motion parameters. Addition of complement did not affect these results except in the antibodies to CD46 in which the reducing action was further amplified.


CONCLUSIONS
Our data suggest that C1-INH, CD55, CD46, and CD59 are present on the sperm surface. These proteins may have biological functions, such as affecting sperm motility, besides the complement regulatory functions. In infertile men and women with antibodies that recognize one or more of these complement regulatory proteins, there may be problems related to poor sperm motility and survival in the reproductive tracts.
Jiang
H
H
Department of Obstetrics and Gynecology, Medical University of South Carolina, Charleston 29425, USA.
Pillai
S
S
D015703:Antigens, CD / Q000378:metabolism*; D018958:CD55 Antigens / Q000378:metabolism*; D018957:CD59 Antigens / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism*; D003174:Complement C1 Inactivator Proteins / Q000378:metabolism*; D003165:Complement System Proteins / Q000378:metabolism*; D006801:Humans; D008297:Male; D051916:Membrane Cofactor Protein; D008562:Membrane Glycoproteins / Q000378:metabolism*; D013081:Sperm Motility / Q000502:physiology*
D015703:Antigens, CD; C497857:CD46 protein, human; D018958:CD55 Antigens; D018957:CD59 Antigens; D003174:Complement C1 Inactivator Proteins; D051916:Membrane Cofactor Protein; D008562:Membrane Glycoproteins; D003165:Complement System Proteins