title: Evidence for apoptosis of the majority of T cells activated in vitro with Actinobacillus actinomycetemcomitans.
abstract: Our previous studies had demonstrated that nearly half of all T cells stimulated with Actinobacillus actinomycetemcomitans are activated within a few hours. However, it was not known whether all of these T cells survive. The aim of the present study was to determine whether the T cells activated in response to A. actinomycetemcomitans undergo apoptosis. To that end, peripheral blood mononuclear cells were cultured at different time points in the presence of A. actinomycetemcomitans. Flow cytometric analysis demonstrated that, following exposure to a preparation of A. actinomycetemcomitans, T cells progressively externalized their plasma membrane phosphatidylserine, as measured by annexin V binding. Approximately half of all T cells bound annexin V by 96 h. During this period, Annexin V-positive T cells also incorporated propidium iodide suggesting loss of membrane integrity. The externalization of phosphatidylserine occurred at a higher rate among activated (CD69+) T cells, where roughly two-thirds became Annexin V-positive. Flow cytometric analysis also demonstrated shrinkage of the Annexin V-positive and propidium iodide-positive T cells. The data presented here provides evidence for the induction of apoptosis among the majority of the T cells responding to A. actinomycetemcomitans.
authors.affiliation: Immune Response Laboratory, Department of Periodontology, School of Dentistry, University of Southern California, 925 West 34th Street, Los Angeles, CA 90089, USA.
authors.forename: A
authors.initials: A
authors.lastname: Nalbant
authors.forename: H H
authors.initials: HH
authors.lastname: Zadeh
mesh_terms: D000328:Adult; D016976:Aggregatibacter actinomycetemcomitans / Q000276:immunology*; D000704:Analysis of Variance; D017304:Annexin A5; D015703:Antigens, CD / Q000276:immunology; D000945:Antigens, Differentiation, T-Lymphocyte / Q000276:immunology; D017209:Apoptosis / Q000276:immunology*; D002462:Cell Membrane / Q000276:immunology; D002470:Cell Survival; D004396:Coloring Agents; D004791:Enzyme Inhibitors; D005260:Female; D005434:Flow Cytometry; D016650:Fluorescein-5-isothiocyanate; D019085:Fluorescent Antibody Technique, Direct; D005456:Fluorescent Dyes; D006801:Humans; D037181:Lectins, C-Type; D007963:Leukocytes, Mononuclear / Q000276:immunology; D008213:Lymphocyte Activation / Q000276:immunology*; D008297:Male; D010718:Phosphatidylserines / Q000276:immunology; D011419:Propidium; D013601:T-Lymphocytes / Q000276:immunology*; D013997:Time Factors; D000099192:CD69 Antigens
chemical_list: D017304:Annexin A5; D015703:Antigens, CD; D000945:Antigens, Differentiation, T-Lymphocyte; D004396:Coloring Agents; D004791:Enzyme Inhibitors; D016650:Fluorescein-5-isothiocyanate; D005456:Fluorescent Dyes; D037181:Lectins, C-Type; D010718:Phosphatidylserines; D011419:Propidium; D000099192:CD69 Antigens