Surgical interventions of the epididymis and vas deferens that cause an obstruction have demonstrated to be the only widely accepted conditions [2–5], demonstrating almost permanently high titers of ASA. Several reports suggest that between 50 and 100 % of men who undergo vasectomy subsequently have sera positive for ASA [4, 8] and the prevalence of ASA in the ejaculate of these men is also extremely high (70–100 %) [5]. It is not that only acquired obstruction of the seminal tract may trigger the formation of ASA. Bronson et al. [9] demonstrated that ASA were detected after the onset of puberty in a cohort of 35 men with cystic fibrosis and congenital bilateral aplasia of the vas deferens (CBAVD).

Following vasectomy, epididymal distension and sperm granuloma formation may result from raised intraluminal pressure. The sperm granuloma is a dynamic structure and a site of much spermatozoal phagocytosis by its macrophage population; however, it is not a permanent finding in patients who have undergone vasectomy [10]. In many species, spermatozoa in the obstructed ducts are destroyed by intraluminal macrophages, and degradation products, rather than the whole sperm getting absorbed by the epididymal epithelium. Humoral immunity against spermatozoal antigens following vasectomy would be secondary to the combination of a constant leak of sperm antigens that by far surmounts all known mechanisms against autoimmunity present in the epididymis and a chronic increase in intraluminal pressure.

The time-course for postvasectomy ASA production does not seem to be triggered exclusively by acute, sudden, and massive reabsorption of spermatozoa after vasectomy but also by slow, gradual, and late sperm antigen reabsorption. Data from a rat model suggests that IgM ASA develop within 2 weeks after vasectomy, decreasing in the next weeks followed by increasing titers of ASA IgG between 8 and 12 weeks [11].

Cellular immunotolerance mechanisms are also implicated in the ASA production of vasectomized patients, as demonstrated by Witkin and Goldstein [12] who described reduced concentrations of T suppressor lymphocytes in their semen when compared with undisturbed vasa.

The immunologic response to spermatozoa is polyclonal, so that the populations of ASA directed against different epitopes vary from individual to individual. As far as the antigenic structure of spermatozoa is concerned, several groups of specific substances have been studied: the ABO groups antigens (Ags), acrosin, HLA Ags, hyaluronidase, protamines, and DNA polymerase [13].

The strength of the ASA formation after vasectomy is variable but there are some patients who have a genetic predisposition to develop ASA [14]. It can be postulated that a breakdown of sperm immune tolerance depends on an individual’s immune responsiveness, the nature of the precipitating event, and the length of exposure of inoculum. The genetic predisposition for the development of an autoimmune sperm reaction has been demonstrated in monozygotic twins where the antisperm immune reaction is triggered by genetic predisposition rather than by the spermatozoa concentration [15].

Still under debate is the location in the genital tract where ASA transuded from serum and locally produced antibodies, respectively, become attached to the surface of the spermatozoa. In spermatozoa retrieved directly from the distal end of the vas in patients undergoing vasovasostomy (VV) and IgG and IgA ASA determined by the immunobead test were present in 78.6 and 32.1 % of the patients [16], respectively, indicating that in these patients, the epididymis would be the primary site of ASA local production and transudation from serum. The question whether the rest of the MRT contributes to ASA deposition in the ejaculate of these patients was addressed by Meinertz et al. [17], who performed the mixed antiglobulin reaction (MAR) for IgG and IgA in the whole ejaculate and the fractions of the split ejaculate of 11 men with history of vasectomy and successful VV. The MAR test revealed almost identical concentrations of ASA in the first and second fractions of the ejaculate. The results suggest that ASA in the ejaculate from VV patients are transuded from serum not only at the epididymal but also at the prostatic and seminal vesicle levels.

In conclusion, chronic obstruction at the level of the vas deferens constitutes a clear risk factor for ASA formation (Table 8.2). In these patients, the most probable site of ASA production is the epididymis; however, once autoimmunization happens transudation of ASA seems to occur also at other levels of the MRT (i.e., seminal vesicles and prostate). The pathophysiology of ASA formation in these patients would involve, among others, an increased intraductal pressure associated with chronic absorption of spermatozoa or sperm fragments and a decrease in the cellular immunomodulatory factors present in the seminal plasma, namely reduced concentrations of T suppressor lymphocytes. It seems logical that any pathologic condition that causes chronic obstruction of the MRT can constitute a risk factor for ASA formation through the same mechanisms.

Infection/inflammation of the MRT is a risk factor for ASA formation through four main mechanisms:

Controversial data exist on the association between inflammation/infection of the MRT and ASA [7]. In a series of 79 infertile patients with inflammatory/infectious diseases of the MRT [5], the comparative results of the two tests for ASA detection in seminal plasma, the MAR and immunobead test, demonstrated no clear role of this association for male infertility. In a second series of 365 patients with documented inflammation/infection of the MRT, such as chronic bacterial prostatitis (CBP), inflammatory chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS), noninflammatory CPPS, chronic urethritis, and chronic epididymitis, again we found no association between ASA formation and these diseases [7]. Also in patients with CP/CPPS, Hoover and Naz did not observe a higher presence of ASA in serum compared to healthy controls [18]. Controversially, Witkin and Toth [19], using an ELISA, reported a 48 % incidence of ASA in seminal plasma of men with a history of urethritis and CBP. Jarow et al. [20] also found a positive association between CP/CPPS and ASA using the gel agglutination assay in serum. Garolla et al. [21] reported significantly higher percentage of ASA in the semen of patients infected with human papillomavirus compared to healthy controls. The number of clinical series dealing with the detection of “significant” ASA levels in seminal plasma of men with inflammation/infection of the MRT is small; the tests used for ASA detection and the positive cut-points for the different methods vary between the different studies. All these factors may explain the fact that the relationship between these two conditions is still debatable.

From a pathophysiological point of view, the absence of a confirmed clinical association between infectious/inflammatory diseases of the MRT and ASA formation would rely on the fact that the four previously mentioned mechanisms, by which these diseases would constitute a risk factor for ASA formation, are not regular findings in patients with these conditions.

Even though both acute and chronic infection/inflammation of the MRT have been claimed as risk factors for partial and total obstruction of the MRT [6, 7], further reports have demonstrated that the link between these two conditions, with the exception of epididymal tuberculosis, is weak [22]. Especially, for CP/CPPS obstructive findings seem to be rare, either not evident or evaluable in less than 10 % [23]. Inflammatory or infectious diseases do not appear to be important causes of obstructions of the MRT [24].

Inflammatory-induced tears of the distal segments of the epididymal duct or efferent duct epithelium may occur in inflammatory/infectious diseases of the MRT breaching the blood–epithelial barriers [12]. This would activate the immunological defense and induce the production of ASA [25, 26]. As there are no sensitive markers for the disruption of the BTB and BEB, it is not possible to evaluate if this event really occurs in patients with inflammation/infection of the MRT or up to what degree it may be present. It is questionable if the presence of leukocytes in seminal fluid could indicate some degree of disruption; however, it is a known fact that the levels of seminal leukocytes in patients with inflammation/infection of the MRT are extremely variable and their exact role and meaning are not clear. Moreover, if this would be the case we [7] and other authors [27–31] have found no association between the presence of ASA and elevation of inflammatory parameters in seminal fluid, such as leukocytes and elastase. Associated with the fact that the disruption of the blood–epithelial barriers is a questionable event in the mentioned diseases, there is also the important fact that a breach of the barrier alone is not enough in many patients to trigger the formation of ASA. This finding was clarified by the studies of Komori et al. [32] and Leonhartsberger et al. [33], in which patients undergoing TESE and organ-sparing surgery for testicular tumors, where certainly a disruption of the BTB occurs, no increased risk of ASA formation was reported.

Even though the significance of white blood cells in the ejaculate remains a matter of debate, several authors have suggested that such cells are important in the modulation of an ASA response, in the sense that the role of the suppressor lymphocyte predominance over helper lymphocytes prevents the formation of ASA. Some reports support the idea that inflammatory/infectious diseases of the MRT would not only not promote granulocyte migration into the MRT but also the activation of B- and T-helper lymphocytes [34], modulating the physiological predominance of T suppressor lymphocytes over helper T lymphocytes [12]. Local production of cytokines at the epididymal epithelium would be an important factor for recruiting lymphocytes into the seminal fluid [35].

In agreement with this theory, Munoz and Witkin [26] postulated that an asymptomatic, undetected Chlamydia trachomatis infection of the MRT may induce the local activation of γδ T lymphocytes that are believed to comprise the first line of immunological defense against infection at mucosal surfaces. Once activated, these would react with those sperm antigens that do not require presentation by MHC class I or class II molecules, resulting in further amplification and activation of γδ T lymphocytes and increased cytokine expression. This in turn would activate gd T lymphocytes in the genital tract and lead to the induction of an autoimmune response to spermatozoa. However, as previously mentioned, several authors [27–30, 36] have reported no relation between the presence of ASA and the number of leukocytes in the ejaculate, suggesting that despite the fact that both abnormalities are manifestations of an immunological response they are not interrelated. Moreover, Barratt et al. [37] reported that in men with ASA the predominance of T helper lymphocytes over T suppressor lymphocytes is very rare. Owing to their similarity, immunological cross-reactivity between antigens of the sperm membrane and Chlamydia trachomatis has also been proposed as a theory to explain the questionable association between infections of the MRT and ASA formation [7]. Immune response against stress proteins (i.e., heat shock proteins (HSP) – essential mammalian and bacterial stress proteins) can be highly cross-reactive. It has been suggested that the antibodies against conserved epitopes on chlamydial HSP 60 may cross-react with those on human HSP 60 and initiate an autoimmune response [38]. However, once again, clinical data fail to detect an association between chlamydial infections and the presence of ASA in seminal plasma [7, 39]. In the hypothetical scenario that inflammatory/infectious diseases of the MRT are associated with ASA formation, for anatomical reasons previously discussed the epididymis would be the most probable site of ASA formation (Table 8.2). However, the prostate gland is another site where a localized immune response can be induced, since prostatic fluids have been identified to contain specific IgA antibody against Escherichia coli and spermatozoa [19]. Some authors suggest that inflammation/infection of the MRT in some men may interfere with the complete closure of prostatic ducts during ejaculation, resulting in leakage of sperm into the prostate gland inducing an immune response [40]. Patients with inflammatory/infectious diseases of the MRT seem to bring together many favorable conditions for ASA formation; however, evidence in clinical studies indicates that the association between these two conditions is extremely weak. A probable explanation for this contradiction would be that all the favorable conditions for ASA formation, supposed to be present in these patients, do not seem to be as important or prevalent as usually considered.

In 1959, Rümke and Hellinka [41] first suggested a probable association between varicocele and ASA; since then, the association between these two entities is a matter of debate. Clinical studies supporting an association have been based in the detection of ASA in serum and in the ejaculate of patients with varicocele. Using enzyme-linked immunoabsorbant assay (ELISA), Golomb et al. [42] and Gilbert et al. [43] found significantly higher levels of ASA in the serum of patients with varicocele vs. controls (90 % vs. 41 % and 32 % vs. 14 %, respectively). Both concluded that varicocele was a risk factor for ASA formation. During the 1990s, other authors [44, 45], testing ASA in the ejaculate by means of immunobead and MAR test, came to the same conclusion. Djadalat et al. [46] using the MAR test found a weak association between varicocele and ASA; moreover, he concluded that even though surgical treatment for varicocele may reduce the ASA level in some patients, it may increase it in others. In the same scenario, Bozhedomov et al. [47] found that after varicocele surgery, ASA developed in 16 % of cases; they also reported that 3 months after surgery patients that were primarily ASA negative improved more sperm parameters compared to patients that were previously ASA negative. Contradicting the previous evidence, Oshinsky et al. [48] and Heidenreich et al. [49] reported in two different series of patients that varicocele is not a risk factor for ASA production. This finding was confirmed by Veräjänkorva et al. [50] who, using the MAR test, analyzed the predisposing factors for male immunological infertility in 508 patients that had been treated for infertility. Patients with a history of varicocele had statistically significant lower level ASA than patients without. In a large study that included 1729 men of reproductive age, varicocele was not significantly associated with ASA formation [51]. Basic research evidence is also controversial: Shook et al. [52] demonstrated in an animal model that a surgically induced varicocele triggers ASA formation. However, Turner et al. [53], working also with surgically induced varicocele model in rats, demonstrated that the BTB was not damaged in these animals, suggesting that the impairment of spermatogenesis in this disease is not immunologically mediated. Interestingly, in patients with varicocele and ASA in the ejaculate these immunoglobulins are also present in testicular biopsies, more specifically inside the seminiferous tubule, suggesting that if in fact there is an association between these two conditions, the most probable site of formation would be the testis [44] (Table 8.2).

Cryptorchidism is defined as a condition in which one or both testes fail to descend to the scrotal position. The incidence of this condition varies from 1.4 to 2.7 % in male births and is increased in premature birth [54]. Several studies have reported an increased incidence of ASA (up to 28 %) in patients with history of cryptorchidism either treated or untreated by orchidopexy [55, 56]. However, most studies include prepuberal population where ASA has been only tested in serum, not addressing the important issue of the presence of ASA in the ejaculate. Moreover, there is a high probability that an undefined percentage of the patients who have undergone orchidopexy develop, as a complication of surgery, some degree of obstruction at the epididymal or ductal level. Those patients have a high probability of ASA formation, but the etiology would be falsely classified to cryptorchidism and not to chronic obstruction.

These later studies oppose to the findings of others [57–59], who evaluated ASA in the serum and ejaculate of patients with history of cryptorchidism, orchidopexy, and testicular biopsy not finding any association between the mentioned conditions and the presence of ASA. Clinical evidence in agreement with this last fact was published by Mirilas et al. [60, 61], who found no evidence of ASA in prepuberal boys with history of cryptorchidism.

In prepuberal population, the clinical evidence is even more conflicting, since before puberty, the absence of mature spermatozoa with its antigenic material should exclude any possible immune reaction against sperm antigens; however, several studies report the presence of ASA in the serum of prepuberal boys with cryptorchidism [55, 62, 63]. Sinisi et al. [64] suggested that in these patients the sperm surface antigens are already present before meiosis and the BTB is either immature or impaired by heat due to the abnormal position. However, evidence in experimental rat models of cryptorchidism demonstrates that the BTB remains competent under this situation [65, 66].

As with other previous conditions, the association between cryptorchidism and ASA remains controversial (Table 8.2). If the association is real and the bias from surgical treatment complications, namely iatrogenic obstruction of the vas deferens, is excluded the most probable site of ASA production in these patients would be the testis.

It seems logical that every condition where the BTB is breached should constitute a clear risk factor for ASA production, since the immune system establishes a direct contact with the antigens present in the sperm surface. Surprisingly, the data are not clear. Kukadia et al. [67] evaluated the presence of ASA in the ejaculate, using the direct immunobead test, in eight patients with a history of severe testicular trauma who underwent surgical exploration. Only one patient had detectable levels of ASA; all other patients were negative for ASA. He concluded that there is no association between these factors. Surgical procedures to the testis have also proved not to be a risk factor for ASA formation; successful TESE [32, 68], open and needle testicular biopsy [69], and organ-sparing surgery for testicular tumor do not constitute a risk factor for ASA production [33]. Surgeries that do not directly compromise the testis but the nearby structures, such as inguinal hernia repair with and without mesh, have also reported no association to ASA formation [70].

Testicular torsion is a surgical emergency, which requires prompt diagnosis and immediate treatment. One of the consequences that patients may face in the follow-up is a compromise of the exocrine testicular function (spermatogenesis) [71]. The generation of ASA because of the rupture of the BTB is claimed to be one of the possible causes of this exocrine impairment. Arap et al. [72] evaluated ASA formation in the ejaculate of 24 patients with history of testicular torsion; 15 were treated with orchiectomy and 9 were treated with orchidopexy. He used 20 proven fertile men as controls and found no significant differences in the ASA levels between patients and controls, regardless of the treatment applied. These results agree with the findings of Anderson et al. [73], who studied a similar population and were unable to find an increased rate of ASA detection in these patients. Identifying the risk factors for ASA production in a population of male patients, Heidenreich et al. [49] also concluded that testicular torsion is not associated with this condition.