Lack of complement activation in the seminal plasma of men with antisperm antibodies associated in vivo on their sperm

A specific and sensitive "sandwich"-type radiolabeled antiglobulin assay (RAA) using monoclonal anti-human C5b-9 neoantigen and polyclonal anti-human C5b-9 was used to evaluate the presence of the in vivo product of human complement (C) activation (SC5b-9) in the seminal plasma (SP) of 19 fertile and 61 infertile men. SP SC5b-9 was detectable in 7 (8.7%; 1 fertile and 6 infertile men) of the 80 men with a range of 10 to 175 ng/ml. Levels of SP SC5b-9 in other men were below the limit of detection (less than 10 ng/ml). Of the 33 infertile men with sperm-associated immunoglobulin (Ig) G and/or IgA, 27 (82%) had undetectable levels of SP SC5b-9 immunoreactivity. There was no correlation between the SP SC5b-9 levels and the degree of sperm-associated IgG (r = 0.086) or IgA (r = 0.23) activity. However, significant deposition of sperm-bound C5b-9 due to autologous C activation was demonstrated by flow cytometry of donor sperm treated with sera from autoimmune men with ASA in their sera and on their sperm. These findings suggest that sperm-bound Ig cannot activate C in SP.

Assessment by fluorescence-activated cell sorting of whether sperm-associated immunoglobulin (Ig)G and IgA occur on the same sperm population

Two-color fluorescence-activated cell sorting of antisperm antibody-positive sperm was used to detect simultaneously the presence of immunoglobulin (Ig)A and IgG antisperm antibodies associated in vivo on a man's sperm. Sperm positive for sperm-associated Ig were analyzed using phycoerythrin-conjugated antihuman IgA and fluorescein isothiocyanate-conjugated antihuman IgG; up to 87% of the same spermatozoa were stained with both labels. Sperm positive for only one of the antisperm antibody isotypes stained up to 90% of a man's sperm with only one fluorochrome. Immunocytochemistry studies revealed similar patterns of sperm binding for sperm-associated IgG and IgA. These results suggest that the sperm antigenic determinants reacting with antisperm IgA and IgG are present on the same sperm population at similar locations on the sperm surface.

Evaluation of antisperm complement-dependent immune mediators in human ovarian follicular fluid

A "sandwich"-type radiolabeled antiglobulin assay using monoclonal anti-C5b-9 neoantigen and polyclonal anti-C5b-9 was used to evaluate the presence of terminal C complexes (SC5b-9 or MC5b-9) in the sera and ovarian follicular fluid (FF) from 45 infertile women. FF SC5b-9 was detectable in all clinical diagnostic categories. The mean SC5b-9 levels in FF and sera were 399 ng/ml (range 75 to 1350 ng/ml) and 798 ng/ml (range 0 to 2700 ng/ml), respectively. Twelve (26.6%) of the 45 FF samples had normal hemolytic C activity, and all FF (n = 44) samples initiated C8/C9-dependent lysis of sensitized sheep E coated with human C1-7. Human plasma IgG antisperm antibodies (ASA) were capable of activating C in 31 (72%) of 43 FF samples as detected by their ability to deposit MC5b-9 on human sperm. Sera from infertile women with ASA in their sera and FF impaired human sperm binding to human zona pellucida and binding and penetration of zona-free hamster oocytes in vitro. The discovery of SC5b-9 and MC5b-9 in ovarian FF implies that the interaction of ASA and C could have a deleterious effect on sperm during in vivo and in vitro sperm-egg interactions in women with antisperm antibodies.

Evaluation of antisperm complement-dependent immune mediators in human ovarian follicular fluid

A "sandwich"-type radiolabeled antiglobulin assay using monoclonal anti-C5b-9 neoantigen and polyclonal anti-C5b-9 was used to evaluate the presence of terminal C complexes (SC5b-9 or MC5b-9) in the sera and ovarian follicular fluid (FF) from 45 infertile women. FF SC5b-9 was detectable in all clinical diagnostic categories. The mean SC5b-9 levels in FF and sera were 399 ng/ml (range 75 to 1350 ng/ml) and 798 ng/ml (range 0 to 2700 ng/ml), respectively. Twelve (26.6%) of the 45 FF samples had normal hemolytic C activity, and all FF (n = 44) samples initiated C8/C9-dependent lysis of sensitized sheep E coated with human C1-7. Human plasma IgG antisperm antibodies (ASA) were capable of activating C in 31 (72%) of 43 FF samples as detected by their ability to deposit MC5b-9 on human sperm. Sera from infertile women with ASA in their sera and FF impaired human sperm binding to human zona pellucida and binding and penetration of zona-free hamster oocytes in vitro. The discovery of SC5b-9 and MC5b-9 in ovarian FF implies that the interaction of ASA and C could have a deleterious effect on sperm during in vivo and in vitro sperm-egg interactions in women with antisperm antibodies.

A radiolabeled antiglobulin assay to identify human cervical mucus immunoglobulin (Ig) A and IgG antisperm antibodies

Antisperm immunoglobulin (Ig) A and IgG antibodies in human cervical mucus (CM) were identified by a radiolabeled antiglobulin assay. Cervical mucus samples from fertile and infertile women were exposed to a 1:3,200 dilution of 2-mercaptoethanol (2-ME), and 5 micrograms of the solubilized CM protein were assayed for the presence of IgA and IgG antisperm and anti-Candida activity by the radiolabeled antiglobulin assay. Purified human secretory IgA and IgG exposed to 2-ME retained the molecular integrity and functional activity of the untreated antibody molecules. CM aliquots collected after high-performance liquid chromatography (HPLC) fractionation were assessed for antisperm antibody activity; antisperm antibody activity was retained in the appropriate IgA or IgG CM fractions. The incidence of CM antisperm antibodies was minimally affected when the radiolabeled antiglobulin assay was performed with a motile sperm population. Approximately 70% of the CM IgA antisperm antibodies were of the IgA1 subclass; CM IgG was primarily of the IgG4 subclass. When Candida antigen was substituted for sperm in the radiolabeled antiglobulin assay, the CM antisperm antibodies were found to be exclusively sperm-specific. These data indicate that the radiolabeled antiglobulin assay using 2-ME to extract CM antibodies is a specific method for the assay of antisperm antibodies in CM.

Immunoreactive human epidermal growth factor in human seminal plasma

We measured immunoreactive epidermal growth factor (EGF) by a homologous RIA in seminal plasma (SP) from 31 fertile and 52 infertile men to determine the relationship between SP EGF levels and total sperm count in the ejaculates. The mean SP EGF levels in fertile and infertile men were 41.7 +/- 21.5 (+/- SD) and 53.1 +/- 30.8 micrograms/L, respectively. Infertile men with sperm-associated immunoglobulin G (n = 9), immunoglobulin A (n = 6), or both (n = 8) had mean SP EGF levels of 48.9 +/- 26.1, 47.9 +/- 17.5, and 56.5 +/- 32.1 micrograms/L, respectively. Seven men with severe oligospermia had a mean SP EGF level of 58.5 +/- 35.9 micrograms/L. There was no correlation (r = 0.14; P greater than 0.05) between SP EGF levels and total sperm counts in these men. Fractionation of SP by high performance liquid chromatography on a size exclusion (TSK G2000 SW) column revealed a single immunoreactive peak with an approximate mol wt of 8000, slightly higher than the mol wt of circulating human EGF (6000). We conclude that SP EGF may be distinct from peripheral plasma EGF.

Quantitation of immunoglobulin G on human sperm

An indirect inhibition assay was devised to quantitate the amount of immunoglobulin molecules on the surface of human sperm. Sperm-associated IgG was used to inhibit competitively 125I-labeled polyclonal anti-human IgG from binding to human IgG affixed to microtissue culture plate wells. Standard curves for the assay were derived by substituting soluble IgG in the supernatant of the tissue culture wells for sperm-associated IgG. The intraassay coefficient of variation was 6.7%; the interassay coefficient of variation was 5.6-21% depending upon the IgG antisperm antibody-positive plasma sample assayed. The assay technique was highly correlated (r = 0.99) with the number of antibody-bound sperm added to the supernatant. When different sperm donors were utilized as an antigen source, the coefficient of variation was 15.6% for positive plasmas and 19.3% for negative plasmas. The indirect inhibition assay showed a strong correlation (r = 0.91) with a previously described radiolabeled antiglobulin assay for sperm-associated IgG.

Distribution of human leukocyte antigen-ABC and -D/DR antigens in the unfixed human testis

The distribution of the major histocompatibility complex (MHC) antigens in the unfixed human testicle was studied by indirect immunofluorescence. Three murine monoclonal antibodies to the common determinants of class I MHC antigens (human leukocyte antigen [HLA]-ABC) and three against class II MHC antigens (HLA-D/DR antigens), respectively, were utilized. No class I MHC antigens were identified on developing testicular germ cells including spermatozoa, but interstitial cells between the seminiferous tubules (including Leydig cells) and blood vessel endothelium expressed the antigen. Class II MHC antigens were not found on any cells within the seminiferous tubules. However, the class II antigen was identified on dendritic-like cells between the seminiferous tubules and on vessel endothelium, although its expression was expectedly limited. These findings indicate that human testicular germ cells express minimal or no MHC antigens.

Effect of repeated washing on sperm-bound immunoglobulin G

The effect of sperm washing on the stability of sperm-bound immunoglobulin G (IgG) antibody derived from plasma from four patients and also IgG bound in vivo on the spermatozoa of four other men was quantitatively evaluated. In the first series of experiments, human spermatozoa were incubated with an IgG antibody-containing plasma and subjected to 18 cycles of sperm washing. In the second set of experiments, spermatozoa from men positive for sperm-bound IgG were subjected to four cycles of sperm washing. The amount of residual antibody bound to a constant number of spermatozoa was quantitated by a radiolabeled antiglobulin assay during and following the washing procedures. There was no significant loss of sperm-bound antibody due to the washing procedures. The results of these studies undermine the utility of sperm washing as an effective treatment of antibody-mediated infertility in men.

ABH blood group antigens in human semen

Human sperm, erythrocytes, and seminal plasma from the blood and semen of 20 men of known ABH, Lewis, and secretor phenotypes were assayed for ABH blood group antigens. A 1:1 correlation was found between the presence of ABH antigens in seminal plasma and on sperm and if the man had a secretor phenotype. Sperm from nonsecretors or from men of dissimilar ABO blood type could adsorb A antigen when incubated with A antigen-containing seminal plasma. The level of ABH antigens in seminal plasma correlated with the level of ABH antigens on the sperm surface. ABH antigens in semen were present only on a minority of spermatozoa as detected by flow cytometry, and the majority of these sperm were not in the swimup fraction. ABH antigens were not present on sperm within the seminiferous tubules of human testicular material. It was hypothesized that ABH antigens found on human sperm were adsorbed from seminal plasma on a minority of the sperm in an ejaculate.

Purification of a human alternative complement pathway inhibitor from hemolymph of larval fall armyworm (Spodoptera frugiperda)

Larval Spodoptera frugiperda hemolymph contains a specific inhibitor of the alternative pathway of human complement. This inhibitor was purified from larval hemolymph (HL) by 50% (NH4)2SO4 precipitation, DEAE-Sephacel chromatography and sequential gel-filtration on Bio-Gel 1.5m, 0.5m and Sephacryl S-200. Purified HL protein (Mr = 110,000) was composed of two Mr 55,000 polypeptide chains. Addition of purified HL protein to human complement resulted in a dose-dependent inhibition of RaRBC lysis and clumping of cells. The protein inhibitor provides a new tool for investigating the regulation of human alternative complement pathway.