Overlap of TCR repertoires among individuals provides the molecular basis for public T cell responses. By deep-sequencing the TCRβ repertoires of CD4+CD8+ thymocytes from three individual mice, we observed that a substantial degree of TCRβ overlap, comprising ∼10–15% of all unique amino acid sequences and ∼5–10% of all unique nucleotide sequences across any two individuals, is already present at this early stage of T cell development. The majority of TCRβ sharing between individual thymocyte repertoires could be attributed to the process of convergent recombination, with additional contributions likely arising from recombinatorial biases; the role of selection during intrathymic development was negligible. These results indicate that the process of TCR gene recombination is the major determinant of clonotype sharing between individuals.

Epidemiologic studies indicated that some infertile men who were infected with Ureaplasma urealyticum displayed positive antisperm antibodies in their serum and/or semen. The purpose of this study was to investigate the possible mechanism of antisperm antibodies production after infection with U. urealyticum and to analyze the relationship between U. urealyticum and infertility. The existence of cross-reactive antigens (61, 50, and 25 kDa) between U. urealyticum and human sperm membrane proteins was confirmed. Among the cross-reactive antigens, the urease complex component UreG of U. urealyticum was determined. By searching the Swiss-Prot protein database, a pentapeptide identity (IERLT) between UreG and human nuclear autoantigenic sperm protein (NASP) was found. Furthermore, using Western blot analysis and enzyme-linked immunosorbent assay, the cross-reaction between the NASP and UreG was verified. Both anti-rUreG antibody and the antiserum against the synthetic peptide NASP393-408 containing the pentapeptide inhibited mouse sperm egg binding and fusion. After immunization by rUreG or the synthetic peptide, 81.2 and 75% female mice became sterile, respectively. The effect on fertility in mice immunized with the synthetic peptide was reversible. These findings proved for the first time that it was feasible to screen antigens for immunocontraceptives from cross-reactive antigens between sperm and microorganisms which induce infertility.Ureaplasma urealyticum lacks cell wall, belongs to the taxonomic class Mollicutes, and is one of the smallest self-replicating prokaryotes (33). Among Mollicutes, U. urealyticum is unique in its ability to hydrolyze urea and requires urea to support growth (16). In 1954, Shepard first isolated U. urealyticum from the urethras of patients with nongonococcal urethritis (29). Since then, there has been intense interest in determining what role U. urealyticum might play in human diseases, particularly in the pathogenesis of genital tract infectious diseases.Because U. urealyticum is an inhabitant of the human lower genital tract, infections are considered to be sexually transmitted and occur more frequently during fertile ages. Although the contributory role of U. urealyticum in infertility has yet to be conclusively established, considerable data have been compiled to support the theory that U. urealyticum can cause infertility (10,11,40,41). Early epidemiologic studies have indicated that U. urealyticum was linked to human reproductive failure on the basis of higher frequencies of isolation from infertile versus fertile couples (11). Friberg and Gnarpe (10) found that U. urealyticum existed in the semen of 76% of the husbands from 50 couples with unexplained infertility. Xu et al. (40) also observed significantly higher frequency of U. urealyticum infection among infertile males (549 of 1,416) compared to fertile controls (34 of 375). Furthermore, they demonstrated that U. urealyticum not only could adhere to the membrane of spermatozoa but also could interfere with sperm motility an...