title: Circannual variation in lymphocyte subsets, revisited.
abstract: BACKGROUND
  Circadian and circannual variations in lymphocyte subsets, especially CD8+ T-lymphocytes, have been reported. This study focuses on CD4+ T-lymphocyte seasonal variation over a 6-year 8-month period.
  
  
  METHODS
  Lymphocyte subsets were quantitated monthly for four healthy individuals from 1986 through 1992 as part of a flow cytometry quality-control program.
  
  
  RESULTS
  In general, there were no significant seasonal changes in the total number of white cells or in total lymphocyte counts. The absolute numbers of CD4+ T-lymphocytes were lowest in summer when the CD8+ T-lymphocytes were highest. Mean CD4+ T-lymphocyte counts were 846, 967, 618, and 695 per microL for Subjects 1 through 4, respectively, in winter and 432, 670, 355, and 766 per microL, respectively, in summer. Two healthy subjects had CD4+ T-lymphocyte counts lower than 300 per microL on one or more occasions during the study period. In three of the four subjects, the percentage of B-lymphocytes in winter was almost double that in summer. In one of the four subjects, no circannual rhythm was observed in these lymphocyte subpopulations.
  
  
  CONCLUSIONS
  The seasonal variation in CD4+ T-lymphocyte counts demonstrated in three healthy individuals over almost 7 years is again of interest in light of renewed consideration of using surrogate tests, such as CD4+ T-lymphocyte counts, to screen for AIDS-like diseases that may be in the blood supply.
authors.affiliation: Sacramento Medical Foundation Center for Blood Research, California.
authors.forename: T G
authors.initials: TG
authors.lastname: Paglieroni
authors.forename: P V
authors.initials: PV
authors.lastname: Holland
mesh_terms: D000328:Adult; D001683:Biological Clocks; D015496:CD4-Positive T-Lymphocytes; D016827:CD8 Antigens / Q000032:analysis; D005260:Female; D006801:Humans; D007958:Leukocyte Count; D016131:Lymphocyte Subsets; D008297:Male; D008875:Middle Aged; D012621:Seasons; D013601:T-Lymphocytes / Q000276:immunology
chemical_list: D016827:CD8 Antigens