title: The healthy rat prostate contains high levels of natural killer-like cells and unique subsets of CD4+ helper-inducer T cells: implications for prostatitis.
abstract: OBJECTIVE
  Chronic nonbacterial prostatitis spontaneously develops in aged Lewis and Wistar rats but not in Sprague-Dawley rats. We report the unique profile of lymphocyte subsets present in the healthy Sprague-Dawley rat prostate.
  
  
  METHODS
  We compared enzymatic and mechanical methods of intraprostatic lymphocyte isolation in healthy 8 to 10-week-old Sprague-Dawley rats. Mechanical isolation was chosen because of its superior preservation of surface antigens. Intraprostatic lymphocyte subsets were analyzed by flow cytometry.
  
  
  RESULTS
  Levels of prostatic alphabetaTCR+ T cells were similar and levels of prostatic B cells were decreased 5 to 10-fold compared with those found in other tissues (p </=0.005). Unexpectedly two-thirds of the total prostatic lymphocytes expressed the natural killer (NK) marker CD161a+. They were divided equally between NK (CD161a+alphabetaTCR) and NKT (CD161a+alphabetaTCR+) cells. Of prostatic CD161a+ cells 50% to 60% were also CD8+. Levels of NKT cells were dramatically lower in other tissues (p </=0.005) and they never accounted for more than 8% of total lymphocytes. The prostate contained lower levels of CD4+ T cells than all tissues except the liver (p </=0.005) and higher levels of CD8+ T cells than any other tissue studied (p </=0.05), resulting in an inverted CD4-to-CD8 ratio. CD45RC+CD4+alphabetaTCR+ T cells and CD161a+CD4+alphabetaTCR+ NKT cells were elevated in the prostate (p </=0.02).
  
  
  CONCLUSIONS
  The healthy rat prostate contains an unusually high proportion of NK and NKT cells. The balance between the CD45RC+CD4+alphabetaTCR+ T cells, which initiate the cell mediated immune response, and CD4+ NKT cells, which can suppress autoimmunity, may be a key in understanding the resistance of Sprague-Dawley rats to chronic nonbacterial prostatitis.
authors.affiliation: Jim and Eilleen Dicke Research Laboratory, Department of Urology, School of Medicine, Case Western Reserve University-University Hospitals of Cleveland, Cleveland, Ohio 44106-4931, USA.
authors.forename: Eugene V
authors.initials: EV
authors.lastname: Vykhovanets
authors.forename: Martin I
authors.initials: MI
authors.lastname: Resnick
authors.forename: Susan Ruth
authors.initials: SR
authors.lastname: Marengo
mesh_terms: D000818:Animals; D007694:Killer Cells, Natural; D008297:Male; D011467:Prostate / Q000166:cytology*; D011472:Prostatitis / Q000276:immunology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D016176:T-Lymphocyte Subsets; D006377:T-Lymphocytes, Helper-Inducer