Human sperm proteome: immunodominant sperm surface antigens identified with sera from infertile men and women.

The objective of this study was to identify those immunodominant sperm antigens recognized by antisperm antibodies (ASA) in the serum samples of infertile men and women. High-resolution two-dimensional gel electrophoresis was employed to separate human sperm proteins using isoelectric focusing or nonequilibrium pH gradient electrophoresis, followed by PAGE. Serum samples from 15 infertile male subjects and 6 infertile female subjects that contained ASA as assayed by the immunobead binding test (IBT) were analyzed by Western blotting followed by enhanced chemiluminescence (ECL). Serum samples from 10 fertile subjects (5 males and 5 females) that were ASA negative by IBT were used as controls. The ECL blots were analyzed by computer scanning to compare the immunoreactivity between serum samples from fertile and infertile subjects and to identify the antigens unique to the sera of the infertile subjects; 98 sperm auto- and iso-antigenic protein spots were recognized by sera from infertile males and females but not from fertile subjects. Based on vectorial labeling with 125I at the sperm surface, a subset of 6 auto- and iso-antigens was identified as possibly relevant to antibody-mediated infertility.     

Antisperm antibodies associated with infertility: properties and encoding genes of target antigens

Infertility among couples of reproductive age is a perplexing condition when the cause is indeterminate. These cases are classified as unexplained infertility. In a subset of subjects, antisperm antibodies with sperm agglutinating and/or immobilizing activities have been detected in the blood or fluids of the reproductive tract. These cases are designated as immunologic infertility although a cause and effect relationship of the antibodies to infertility has not been established. In this review, seven target sperm antigens to antibodies associated with infertility and their encoding genes are described. The antisperm antibodies (ASAs) examined were obtained from infertile women or were monoclonal antibodies (mAb) raised against human sperm proteins. All the ASAs studied possessed potent sperm agglutinating and/or immobilizing activities. The target antigens were isolated from human and other mammalian sperm, and the encoding genes identified. The seven antigens are YWK-II, BE-20, rSMP-B, BS-63 (nucleoporin-related), BS-17 (calpastatin), HED-2 (zyxin), and 75- kDa. Each antigen is a distinct and separate entity and is produced by different cells of the reproductive tract, (e.g., germ cells, epididymal epithelial cells, and Sertoli cells). No single predominant target component has been found to interact with the ASAs. It is proposed that immunologic infertility is the consequence of the combined actions of multiple ASAs in immobilizing and/or agglutinating spermatozoa, blocking spermegg interaction, preventing implantation, and/or arresting embryo development.     

Identification of human sperm surface glycoproteins recognized by autoantisera from immune infertile men, women, and vasectomized men

To identify the surface antigens of human sperm recognized by antisera from immune infertility patients and vasectomized men, we labeled sperm surface proteins with 125I- and used patient antisera for immunoprecipitation. Sera were studied from 27 infertile males, 18 infertile females, and 4 vasectomized males, each possessing anti-sperm antibodies detected by immunobead binding. Sera from different infertile males, different infertile females, and vasectomized males were remarkably similar in their surface antigen recognition. The different sera specifically immunoprecipitated the same small group of 125I-labeled surface proteins, which included polypeptides in the region 90 kDa, 40-45 kDa, and 26 kDa. Treatment with N-glycanase showed that the proteins of 90 kDa, 40-45 kDa, and 26 kDa were glycoproteins with N-linked carbohydrate. The immunoprecipitated 125I-labeled proteins and the total extract of 125I-labeled surface proteins were compared on two-dimensional (2D) gels. The results show the 90 kDa polypeptide is a major sperm surface component, whereas 40-45 kDa and 26 kDa polypeptides are minor components. The 2D gel comparison also indicates that 90 kDa, 40-45 kDa, and 26 kDa are a small subset of the total ensemble of sperm surface proteins. Clinical data suggest antibodies to these few proteins interfere with sperm function.     

Anticorps anti-spermatozoïdes: techniques de dépistage et interprétation des résultats

Since the first publication on the detection of sperm-agglutinating antibodies in infertile men, multiple assays have been described. The most useful tests are able to detect antibodies bound to the sperm membrane of motile spermatozoa. The immunobeads test (IBT) is considered to be the most advantageous in terms of its sensitivity, the low incidence of false-positive results, and its ability to localize antibodies of different immunoglobulin classes on the sperm surface. The IBT assay can be used in parallel with the mixed antiglobulin reaction (MAR), to detect sperm-associated antibodies in the ejaculates of infertile men, the most rational way to test for antisperm antibodies (ASA) in males. In view of the high level of agreement between the two assays, MAR, the easier of the two, may be used as a first step in the detection of these antibodies. A positive MAR must be confirmed by IBT, as this assay is more specific for the detection of IgA antibodies. The clinical significance of sperm-associated antibodies is usually established according to the proportion of motile spermatozoa coated with immunobeads, its class and its localization on the sperm surface. However, binding of immunobeads does not provide any information about the antigens against which the antibodies are directed. As the functional effects of sperm-associated antibodies may vary as a function of their antigenic specificities, other assays, using purified fertilization related antigens, are necessary to establish, for each individual, the specific impact of the antibodies on the fertilization process. The indirect IBT assay has recently become the most widely used test to detect the various classes of ASA in serum and cervical mucus of infertile women and in the serum and seminal fluid of infertile men, in combination with the direct assay described above. However, in most laboratories, it is performed with only one dilution of the biological fluid tested, usually a low dilution, so that antibody levels of no significance for fertility could be detected. This may explain a recente debate (Human Reprod, 1999) on the significance of ASA as a cause of infertility. At present, and in the absence of standardized assays able to identify the antigens involved in each individual immune reaction, antibody assays, as detected by the IBT assay, in the serum and/or genital secretions of infertile subjects might provide useful clinical guidance.     

Immune regulatory molecules as modifiers of semen and fertility: A review

Declining fertility rates in both human and animals is a cause for concern. While many of the infertility cases are due to known causes, idiopathic infertility is reported in 30% of the infertile couples. In such cases, 18% of the infertile males carry antisperm antibodies (ASAs). Such data are lacking in livestock, wherein 20–30% of the animals are being culled due to low fertility. In males, the blood–testis barrier (BTB) and biomolecules in the semen provide an immuno‐tolerant microenvironment for spermatozoa as they traverse the immunologic milieu of both the male and female reproductive tracts. For example, insults from environmental contaminants, infections and inflammatory conditions are likely to impact the immune privilege state of the testis and fertility. The female mucosal immune system can recognize allogenic spermatozoa‐specific proteins affecting sperm kinematics and sperm‐zona binding leading to immune infertility. Elucidating the functions and pathways of the immune regulatory molecules associated with fertilization are prerequisites for understanding their impact on fertility. An insight into biomolecules associated with spermatozoal immune tolerance may generate inputs to develop diagnostic tools and modulate fertility. High‐throughput sequencing technologies coupled with bioinformatics analyses provides a path forward to define the array of molecules influencing pregnancy outcome. This review discusses the seminal immune regulatory molecules from their origin in the testis until they traverse the uterine environment enabling fertilization and embryonic development. Well‐designed experiments and the identification of biomarkers may provide a pathway to understand the finer details of reproductive immunology that will afford personalized therapies.     

Inhibition of in vitro fertilization by mouse anti-mouse sperm sera and preliminary antigen identification

Antisperm antibodies are implicated as one causative factor of infertility, but the target antigens have not been identified. Immune responses to sperm antigens are qualitatively variable even within a single mouse strain. We took advantage of this variability and immunized individual female mice to allogeneic sperm to reflect their natural exposure during mating. We determined the ability of the individual sera to inhibit in vitro fertilization and to bind to sperm antigens separated by electrophoresis. Compared to preimmune sera, four of five immune sera significantly inhibited in vitro fertilization. The serum from individual mice bound variable panels of sperm antigens. By comparing the panels, we identified two polypeptides with molecular weights of 40,000 and 44,000 that were bound by all sera. We propose that these molecules may be good candidates for further investigation of the immunoprophylaxis of pregnancy.     

Molecular identities of human sperm proteins reactive with antibodies in sera of immunoinfertile women

Antisperm antibodies (ASA) can cause infertility in both men and women. It is important to delineate the sperm antigens against which these ASA are directed. Sperm proteins were separated by 2D gel electrophoresis and transferred to nitrocellulose membrane and incubated with sera from fertile women or immunoinfertile women having ASA. The corresponding immunoreactive peptide spots were cored from the gel and analyzed by the two-dimensional (2D) gel electrophoresis/matrix-assisted laser desoprtion ionization-time of flight-mass spectrometry and liquid chromatography-mass spectrometry (MALDI-TOF-MS/LC-MS). A total of 68 spots belonging to 38 different proteins and their isomers were identified. Fourteen of these proteins and their isomers reacted with both the fertile and immunoinfertile sera. Twenty-four of these proteins reacted specifically only with the immunoinfertile sera and not with the fertile sera. Among them was a novel protein designated as a hypothetical protein FLJ32704 (accession # Q96MA6). An immunodominant sequence (amino acid 151-159) of this protein was identified and a nonamer peptide based upon this sequence (IQTLG1TPR) was synthesized and examined for its immunoreactivity. This synthetic peptide reacted with 90% (36/40) of immunoinfertile sera and not with any of the fertile sera (0/40) in the enzyme-linked immnosorbent assay (ELISA). In conclusion, using the 2D gel electrophoresis/MALDI-TOF-MS/LC-MS procedure, we have identified several known and at least one novel antigen against which the antibodies are present in sera of immunoinfertile but not fertile women. Some of these antigens may find applications in specific diagonsis and treatment of infertility/immunoinfertility, and in the development of new generation of contraceptive modalities including contraceptive vaccines.     

Analysis of sperm antigens by sodium dodecyl sulfate gel/protein blot radioimmunobinding method

A radioimmunobinding method based on the blotting of renatured proteins from sodium dodecyl sulfate gels on to nitrocellulose filter papers was developed to analyze the sperm antigens that elicit serum anti-sperm antibodies. In rabbits, serum anti-sperm antibodies were raised by immunization with homologous epididymal spermatozoa mixed with complete Freund's adjuvant. The raised antisera from either male or female rabbits were shown to react with three major sperm protein bands on sodium dodecyl sulfate gels with the corresponding molecular weights of about 70,000 ± 5000, 14,000, and 13,000, respectively. In humans, the monoclonal antibodies against human sperm were raised by a hybridoma technique. Out of six independent hybrid cell lines that were generated, three of them were shown to secrete immunoglobulins that react with the same two protein bands on sodium dodecyl sulfate gels, which have the approximate molecular weight of 10,000. The same procedure was also used to analyze human serum samples that were shown to contain anti-sperm antibodies by the known techniques. Unique sperm antigens that elicit anti-sperm antibodies in humans were identified and correlated. The results of this study suggest that sodium dodecyl sulfate gel/protein blot radioimmunobinding method may be a sensitive and useful tool for the study of sperm antigens that elicit autoimmune responses and their association with human infertility.     

Activation of human complement by IgG antisperm antibody and the demonstration of C3 and C5b-9-mediated immune injury to human sperm

To investigate the role of C in the pathogenesis of antisperm antibody (ASA)-mediated infertility, we evaluated the binding and biologic effects of antisperm IgG and autologous C on human sperm. A flow cytometric assay using motile sperm as a target for IgG ASA+ (n = 30) and ASA- (n = 5) sera was developed for the concomitant detection of sperm-bound IgG and the initial (C3d) and terminal (C5b-9) C components on the surface of human sperm. Of the 30 IgG ASA+ sera evaluated by flow cytometry, 15 (50%) and 22 (73.3%) sera were also positive for sperm-bound C3d and C5b-9, respectively. Monomeric IgG purified from C-fixing ASA+ serum was able to bind to sperm and induced deposition of C3 on the sperm surface in the presence of human C. Incubation of motile sperm with C-fixing immune sera resulted in a significant loss (43 to 87%) of motility associated with characteristic C5b-9-induced alterations in sperm morphology leading ultimately to sperm lysis. When motile sperm were cocultured with purified polymorphonuclear leukocytes (PMN) in the presence of C-fixing immune sera, the binding of sperm heads to the PMN resulted in the formation of sperm rosettes, whereas non C-fixing or control sera had no such effect. Transmission electron microscopy of thin sections of the rosettes revealed ingestion of the sperm by the human PMN. These data suggested that 1) antibody bound to sperm is capable of activating autologous C by the classical pathway; 2) binding of both IgG and C proteins initiates C3-mediated sperm binding to PMN and sperm inactivation by deposition of membrane attack complex (MC5b-9) of C; and 3) concomitant detection of sperm-bound IgG, C3d, and C5b-9 may serve as an indicator of C-fixing cytotoxic ASA in the sera of infertile couples.     

Sperm cells induce distinct cytokine response in peripheral mononuclear cells from infertile women with serum anti-sperm antibodies

Background and Aims

Anti-sperm antibodies in can markedly reduce the likelihood of natural conception. The etiology of this anti-sperm immunity in human females is unknown. We compared the cytokine response of peripheral blood mononuclear cells (PBMCs) from infertile patients with or without anti-sperm antibodies (ASA) and fertile women.

Methodology/Principal Findings

We cultivated the PBMCs together with sperm antigens (whole cells or cell lysate), and screened the supernatants for 40 cytokines by antibody array. When stimulated with whole sperm cells, the PBMCs from patients with ASA produce less IL-3, IL-11, IL-13, ICAM-1, GCSF and more IL-2, IL-4 and IL-12p70 as compared to healthy women. PBMCs from patients with ASA produce typically less IL-13, IL-7, IL-17 and MIG, and more MIP-1β and IL-8, as compared to PBMCs from patients without ASA. In response to sperm cell lysate, PBMCs from infertile women without ASA respond initially by increase in production of growth factors (GCSF, GM-CSF and PDGF-BB) followed by increase in chemokines (e.g. IL-8, MCP-1 and MIP-1β).

Conclusions

Cellular immune responses to sperm antigens, measured by production of cytokines, differ among infertile women with ASA, infertile women without ASA and healthy women. This difference could play an important role in the initial steps of the infertility pathogenesis.     

Use of larval, parasitic female and egg antigens from Strongyloides venezuelensis to detect parasite-specific IgG and immune complexes in immunodiagnosis of human strongyloidiasis

The aim of this study was to use larval, parasitic female and egg antigens from Strongyloides venezuelensis to detect parasite-specific IgG and immune complexes in human serum samples by enzyme-linked immunosorbent assay (ELISA). In total, 95 serum samples were analysed, consisting of 30 patients harbouring S. stercoralis larvae, 30 healthy subjects and 35 patients with other parasites. Sensitivity, specificity and diagnostic efficiency were calculated. A significant statistical difference was found in the detection of immune complexes and antibodies in patients harbouring S. stercoralis larvae from larval and eggs antigens, with higher positivity using larval antigen. The larval antigen showed the highest values for sensitivity, specificity and diagnostic efficiency in ELISA from detection of immune complexes. For the first time we used IgG anti-larvae, IgG anti-parasitic females or IgG anti-eggs for immune complex detection. We concluded that the association of antibody and immune complex detection could be used in the diagnosis of human strongyloidiasis.     

Immunoglobin-binding proteins in human placenta]

Phenomena of the binding of poor-soluble placenta proteins (PSPP) with pregnant women sera IgG as well as placenta blood IgG were studied. PSPP were extracted from the placenta tissue, washed out from soluble proteins, by the use of 3M KCl solution containing 0.005 M PMSF. PSPP were separated by the use of two-dimensional isoelectrofocusing and SDS-PAG electrophoresis and more than 30 different polypeptides were visualized. Having used various ELISA procedures with pregnant women sera IgG, placenta blood IgG as well as its Fab and Fc-fragments we have shown that both the receptor-type and the antigen-antibody-like interaction of PSPP took place. Both the polypeptide compositions and the isoelectrofocusing points ranges of the antigen-antibody-like interacting IgG-binding PSPP were determined by the use of the peroxidase conjugated Fab-fragments of the placenta blood IgG.     

Antifertility effects in rats actively immunized with 80 kDa human semen glycoprotein.

A 80 kDa human sperm antigen has been identified using the serum of an infertile woman having circulating antisperm antibodies. The antigen was then purified to homogeneity by gel permeation chromatography using HPLC (protein PAK-125 column) system and on FPLC (superose-12 column) system. The antigen was found to be a glycoprotein. The antigen was mainly localized in the postacrosomal region of the human sperm, while it was localized in the head region of the rat sperm as demonstrated by immunofluorescent staining. The presence of this antigen was also demonstrated in the human prostate and endometrium and in the rat testis; epididymis and the prostate by immunocytochemical staining. The purified protein upon active immunization in female rats caused infertility in 100 percent animals. While in male rats it caused infertility in 90 percent animals. On morphometric analysis of testicular tissue it was observed that there was no significant change in spermatogonia and spermatocytes, but significant decrease in spermatids and sperm number as well as daily sperm production in the immunized male rats. The epididymal spermatozoa were markedly reduced in number and were largely found to be agglutinated. The results suggest that 80 kDa human sperm antigen appears to be a suitable candidate for immunocontraception both in male and female.     

Solubilization of IgG-binding proteins from group A and G streptococci

The release of IgG-binding proteins from the cell surface of streptococcal strains AR-1 and G148 with various proteolytic enzymes, acid, alkali or SDS was investigated. The IgG-binding proteins were purified by affinity chromatography using IgG-Sepharose Fast Flow. After SDS-polyacrylamide gel electrophoresis and immuno-electroblotting the major proteins identified varied in relative molecular mass from 15,000 to 65,000 depending on the solubilizing agent used. The results showed that solubilization with trypsin gave the highest yield of IgG-binding proteins, that strain G148 yielded about twice the amount of protein as strain AR-1, and that elastase released an IgG-binding protein of high relative molecular mass of 65,000.     

Vaccine for human contraception targeting sperm Izumo protein and YLP12 dodecamer peptide

There is an urgent need to develop a better method of contraception which is non‐steroidal and reversible to control world population explosion and unintended pregnancies. Contraceptive vaccines (CV), especially targeting sperm‐specific proteins, can provide an ideal contraceptive modality. Sperm‐specific proteins can induce an immune response in women as well as men, thus can be used for CV development in both sexes. In this article, we will review two sperm‐specific proteins, namely Izumo protein and YLP₁₂ dodecamer peptide. Gene‐knockout studies indicate that Izumo protein is essential for sperm–egg membrane fusion. Vaccination with Izumo protein or its cDNA causes a significant reduction in fertility of female mice. The antibodies to human Izumo inhibit human sperm penetration assay. Recently, our laboratory found that a significant percentage of infertile women have antibodies to Izumo protein. The second sperm‐specific protein is YLP₁₂, a peptide mimetic sequence present on human sperm involved in recognition and binding to the human oocyte zona pellucida. Vaccination with YLP₁₂ or its cDNA causes long‐term, reversible contraception, without side effects, in female mice. Infertile, but not fertile, men and women have antibodies to YLP₁₂ peptide. Our laboratory has isolated, cloned, and sequenced cDNA encoding human single chain variable fragment (scFv) antibody from infertile men which reacts with YLP₁₂ peptide. The human YLP₁₂ scFv antibody may provide a novel passive immunocontraceptive, the first of its kind. In conclusion, sperm‐specific Izumo protein and YLP₁₂ peptide can provide exciting candidates for antisperm CV development.     

以人精子抗原消化道免疫后的体液免疫反应

The inbred Balb/c and C57 mice, and the outbred Swiss Webster mice were intragastrointestinally immunized with human sperm antigens. The lymphocytes from the spleen, mesenteric lymph node (MLN), Peyer's patch (PP) and uterus or epididymis were isolated and cultured. The lymphocyte-secreting antisperm IgG and IgA and the antisperm antibodies in the gut wash and serum were determined with enzyme-linked immunosorbent assay (ELISA). In the Balb/c and Swiss Webster mice, the immune responses to sperm have shown to be stronger than that in C57, stronger in female than in male. The antigenicity of sperm membrane extracts seems to be higher than that of whole sperm. Antisperm antibodies secreted by lymphocytes from the epididymis and uterus have demonstrated to be detectable. For stimulation of the local immune response, the intra-PP and intralumina immunizations are more effective than others.     

以人精子抗原消化道免疫后的体液免疫反应

在Balb/c、C57和昆明鼠的消化道不同部位以人精子抗原免疫后,取其脾、肠系膜淋巴结、Peyer氏淋巴小结及子宫或附睾中的淋巴细胞进行培养。以ELISA法测定了这些部位的淋巴细胞所分泌的以及免疫小鼠肠道冲洗液和血清中的抗精子抗体。结果提示,Balb/c和昆明鼠抗精子免疫反应较强,而且雌性强于雄性。免疫部位以小肠及Peyer氏淋巴小结内注射的免疫效果较好,不仅可引起消化道局部免疫反应,而且子宫、附睾等生殖道组织也有淋巴细胞分泌抗精子抗体。     

Anticardiolipin antibodies in women with unexplained infertility

Concept of autoimmune basis of infertility is still controversial, particularly regarding the presence of non-organ specific autoantibodies. Non-organ specific anticardiolipin (aCL) and antithyroglobulin (TgAt) antibodies were detected in infertile women. Both partners were evaluated according to the criteria of The American Society for Reproductive Medicine. All the results were normal in cases of unexplained infertility. Antisperm antibodies (ASA) were determined by a mixed antiglobulin reaction (MAR) and the Kibrick agglutination assay, aCL by commercial ELISA, TgAt by commercial RIA. Fertile women had children. Subjects were grouped in fertile (n=27), infertile (n=65), and cases of unexplained infertility (n=42). In fertile women, aCL was below the negative cut-off value (100 %), while women with unexplained infertility were positive in 23.8 %. Anticardiolipin (aCL) antibodies were detected in 21.5 % of infertile patients, most of them with unexplained infertility (15.4 %). Other positive women had partners with ASA (4.6 %), or exhibited a negative postcoital test (1.5 %). In this study aCL were not detected in women with ASA. TgAt incidence was increased in infertile (20 %) and unexplained infertility group (21.4 %) compared to the fertile controls (18.5 %). Increased incidence of aCL and TgAt in infertile women supports the contention that these autoantibodies contribute to the infertility     

Isolation and characterisation of two sperm membrane proteins recognised by sperm-associated antibodies in infertile men

Antisperm antibodies eluted from the surface of spermatozoa obtained from infertile men recognised several common epitopes. We tested whether these epitopes were relevant to fertility by isolating the immunodominant 37/36 and 19/18 protein zones. These protein zones were cut out of preparative slab gels and electro-eluted. The isolated proteins, P36 and P18, were used for biochemical characterisation and to produce specific antibodies in rabbits. The specific reactivity of P36 and P18 with WGA and AAL lectins, respectively, indicated the presence of lactosaminyl structures with sialic acid termini in P36 and of fucosylated residues in P18. Isoelectric focusing showed that the two proteins consist of several polypeptides. Some of these polypeptides were recognised by both human and rabbit antibodies: the pl of these epitopes was around 5.5 for P36 and 8.3-10.3 for P18. Rabbit antibodies detected the corresponding proteins on the sperm heads of methanol-fixed and of live acrosome-reacted spermatozoa. Anti-P36 antibodies bound mainly to the equatorial segment. They reduced the binding and, consequently, the penetration of zona-free hamster oocytes by human spermatozoa. Anti-P18 antibodies gave more diffuse staining of the acrosomal and post-acrosomal regions and reduced sperm-oocyte penetration without a significant effect on sperm binding. These results suggest that P36 and P18 antigens located in different compartments of the sperm head may participate in the sperm-oolemma interaction. We are currently investigating the physiological role of these antigens by sequencing the proteins isolated from the gels.     

Evidence for functional heterogeneity in IgG Fc-binding proteins associated with group A streptococci

A number of group A streptococcal isolates have been compared for their nonimmune reactivity with each human IgG subclass, and rabbit, pig, or horse IgG. The results obtained demonstrate considerable heterogeneity in the expression of type II IgG-binding proteins among and within group A isolates. Extraction and analysis of type II IgG-binding proteins from selected strains demonstrate the existence of five functionally distinct IgG-binding proteins. The type IIo IgG binding protein displayed the greatest range of reactivities, binding to all four human IgG subclasses, and rabbit, pig, and horse IgG. A variant of this protein, designated type II'o, bound all four human subclasses and rabbit IgG, but failed to react with pig or horse IgG. A type IIa protein was recovered from certain group A strains which bound human IgG1, IgG2, IgG4, as well as reacting with rabbit, pig, and horse IgG. A functionally related type IIc activity that displayed all of the reactivities of the type IIa protein but did not bind with human IgG2 was also identified. The final functional form of group A IgG-binding protein, the type IIb protein, bound exclusively to human IgG3. Comparison of these functionally different type II IgG-binding proteins demonstrated no simple structure-function relationship. These studies underscore the heterogeneity of type II Ig-binding proteins expressed by different group A streptococci and document that a single strain can change its pattern of expression of type II IgG-binding protein both quantitatively and qualitatively.