Egress of sperm autoantigen from seminiferous tubules maintains systemic tolerance
Kenneth S.K. Tung, … , C. Yan Cheng, Erwin Goldberg
Kenneth S.K. Tung, … , C. Yan Cheng, Erwin Goldberg
Published February 20, 2017
Citation Information: J Clin Invest. 2017;127(3):1046-1060. https://doi.org/10.1172/JCI89927.
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Research Article Immunology Reproductive biology

Egress of sperm autoantigen from seminiferous tubules maintains systemic tolerance

Abstract

Autoimmune responses to meiotic germ cell antigens (MGCA) that are expressed on sperm and testis occur in human infertility and after vasectomy. Many MGCA are also expressed as cancer/testis antigens (CTA) in human cancers, but the tolerance status of MGCA has not been investigated. MGCA are considered to be uniformly immunogenic and nontolerogenic, and the prevailing view posits that MGCA are sequestered behind the Sertoli cell barrier in seminiferous tubules. Here, we have shown that only some murine MGCA are sequestered. Nonsequestered MCGA (NS-MGCA) egressed from normal tubules, as evidenced by their ability to interact with systemically injected antibodies and form localized immune complexes outside the Sertoli cell barrier. NS-MGCA derived from cell fragments that were discarded by spermatids during spermiation. They egressed as cargo in residual bodies and maintained Treg-dependent physiological tolerance. In contrast, sequestered MGCA (S-MGCA) were undetectable in residual bodies and were nontolerogenic. Unlike postvasectomy autoantibodies, which have been shown to mainly target S-MGCA, autoantibodies produced by normal mice with transient Treg depletion that developed autoimmune orchitis exclusively targeted NS-MGCA. We conclude that spermiation, a physiological checkpoint in spermatogenesis, determines the egress and tolerogenicity of MGCA. Our findings will affect target antigen selection in testis and sperm autoimmunity and the immune responses to CTA in male cancer patients.

Authors

Kenneth S.K. Tung, Jessica Harakal, Hui Qiao, Claudia Rival, Jonathan C.H. Li, Alberta G.A. Paul, Karen Wheeler, Patcharin Pramoonjago, Constance M. Grafer, Wei Sun, Robert D. Sampson, Elissa W.P. Wong, Prabhakara P. Reddi, Umesh S. Deshmukh, Daniel M. Hardy, Huanghui Tang, C. Yan Cheng, Erwin Goldberg

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Figure 4

EAO of Treg-depleted DEREG mice is characterized by M1-like macrophage infiltration, immune complex deposition, and disrupted Sertoli cell barrier.

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EAO of Treg-depleted DEREG mice is characterized by M1-like macrophage i...
(A) Testis weight at 8 weeks after DT treatment. (B) Increased interstitial F4/80+ macrophages (red) and reduced seminiferous tubule diameter and ZAN+ spermatids (green) in DEREG mice with EAO compared with control mice. Original magnification, ×100. (C) Most macrophages of control mice have the characteristic phenotype of M2 macrophages, including the expression of IL-4Rα, CD206, and F4/80 (left), whereas macrophages of Treg-depleted DEREG mice have an M1-like phenotype of high iNOS and MHC class II expression (right); data are expressed as a ratio of absolute numbers (right), where each symbol represents cells from 2 testes of 1 mouse. (D) Mouse IgG immune complexes (green) in the DEREG mouse testes with EAO are located both outside and inside seminiferous tubules relative to the occludin+ Sertoli cell barrier (red). Original magnification, ×300. (E) Biotin (red) exclusion assay in testes of control mice (top) and Treg-depleted DEREG mice (bottom). Original magnification, ×100. (F) Western blot analysis of extractable tight junction proteins of the Sertoli cell barrier from testes of control and Treg-depleted DEREG mice. This is a composite data set of 8 parallel blots wherein 4 control and Treg-depleted DEREG mouse testis samples were analyzed by using corresponding specific Abs in a single experimental session to avoid interexperimental variations. (G) IF staining of murine IgG (green) and rabbit IgG (red) in the testis of a DEREG mouse with EAO at 19 hours after i.p. injection of rabbit Abs to LDH3. Note rabbit (red) and mouse (green) immune complexes were admixed or colocalized inside the seminiferous tubule (arrow). Dotted line, seminiferous tubule boundary. Original magnification, ×800. Data are from 2–12 independent experiments. *P < 0.05; ***P < 0.001, Mann-Whitney U test (A and C).