title: Endogenous analgesia mediated by CD4(+) T lymphocytes is dependent on enkephalins in mice.
abstract: T cell-derived opioids play a key role in the control of inflammatory pain. However, the nature of opioids produced by T cells is still matter of debate in mice. Whereas β-endorphin has been found in T lymphocytes by using antibody-based methods, messenger RNA (mRNA) quantification shows mainly mRNA encoding for enkephalins. The objective of the study is to elucidate the nature of T cell-derived opioids responsible for analgesia and clarify discrepancy of the results at the protein and genetic levels.
  
  
  
  CD4(+) T lymphocytes were isolated from wild-type and enkephalin-deficient mice. mRNA encoding for β-endorphin and enkephalin was quantified by RT-qPCR. The binding of commercially available polyclonal anti-endorphin antibodies to lymphocytes from wild-type or enkephalin knockout mice was assessed by cytofluorometry. Opioid-mediated analgesic properties of T lymphocytes from wild-type and enkephalin-deficient mice were compared in a model of inflammation-induced somatic pain by measuring sensitivity to mechanical stimuli using calibrated von Frey filaments.
  
  
  
  CD4(+) T lymphocytes expressed high level of mRNA encoding for enkephalins but not for β-endorphin in mice. Anti-β-endorphin polyclonal IgG antibodies are specific for β-endorphin but cross-react with enkephalins. Anti-β-endorphin polyclonal antibodies bound to wild-type but not enkephalin-deficient CD4(+) T lymphocytes. Endogenous regulation of inflammatory pain by wild-type T lymphocytes was completely abolished when T lymphocytes were deficient in enkephalins. Pain behavior of immune-deficient (i.e., without B and T lymphocytes) mice was superimposable to that of mice transferred with enkephalin-deficient lymphocytes.
  
  
  
  Rabbit polyclonal anti-β-endorphin serum IgG bind to CD4(+) T lymphocytes because of their cross-reactivity towards enkephalins. Thus, staining of T lymphocytes by anti-β-endorphin polyclonal IgG reported in most of studies in mice is because of their binding to enkephalins. In mice, CD4(+) T lymphocytes completely lose their analgesic opioid-mediated activity when lacking enkephalins.
authors.affiliation: IRSD, Université de Toulouse, INSERM, INRA, ENVT, UPS, Toulouse, France.
authors.forename: Lilian
authors.initials: L
authors.lastname: Basso
authors.affiliation: IRSD, Université de Toulouse, INSERM, INRA, ENVT, UPS, Toulouse, France.
authors.forename: Jérôme
authors.initials: J
authors.lastname: Boué
authors.affiliation: CPTP, Université de Toulouse, CNRS, INSERM, UPS, Toulouse, France.
authors.forename: Karim
authors.initials: K
authors.lastname: Mahiddine
authors.affiliation: IRSD, Université de Toulouse, INSERM, INRA, ENVT, UPS, Toulouse, France.
authors.forename: Catherine
authors.initials: C
authors.lastname: Blanpied
authors.affiliation: IRSD, Université de Toulouse, INSERM, INRA, ENVT, UPS, Toulouse, France.
authors.forename: Sébastien
authors.initials: S
authors.lastname: Robiou-du-Pont
authors.affiliation: IRSD, Université de Toulouse, INSERM, INRA, ENVT, UPS, Toulouse, France.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Vergnolle
authors.affiliation: IRSD, Université de Toulouse, INSERM, INRA, ENVT, UPS, Toulouse, France.
authors.forename: Céline
authors.initials: C
authors.lastname: Deraison
authors.affiliation: IRSD, Université de Toulouse, INSERM, INRA, ENVT, UPS, Toulouse, France. gilles.dietrich@inserm.fr.
authors.forename: Gilles
authors.initials: G
authors.lastname: Dietrich
mesh_terms: D000595:Amino Acid Sequence; D000698:Analgesia / Q000379:methods*; D000818:Animals; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology / Q000378:metabolism*; D004745:Enkephalins / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D008297:Male; D051379:Mice; D057507:Mice, 129 Strain; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D010146:Pain / Q000276:immunology / Q000378:metabolism* / Q000517:prevention & control*; D010147:Pain Measurement / Q000379:methods*; D011817:Rabbits; D011897:Random Allocation
chemical_list: D004745:Enkephalins
keywords: Enkephalin; Inflammation; Pain; T lymphocytes; β-endorphin