Characterization of antigen-specific CD4+ effector T cells in vivo: immunization results in a transient population of MEL-14-, CD45RB- helper cells that secretes interleukin 2 (IL-2), IL-3, IL-4, and interferon gamma.
In previous studies we demonstrated that, following activation by mitogens or alloantigens, helper T cell precursors proliferate and differentiate in vitro to produce a population of effector cells that secrete high titers of lymphokines upon restimulation. In this report, we demonstrate that a similar effector population develops in vivo following primary antigen stimulation. When restimulated with specific antigen in vitro, CD4+ T cells from mice primed 5 to 7 days previously by subcutaneous administration of keyhole limpet hemocyanin (KLH) in adjuvant, produced high levels of interleukin 2 (IL-2), IL-4, and IL-3, and little or no interferon gamma (IFN-gamma) or IL-5. The effector T cells provided excellent helper activity for in vitro antibody responses of 4-hydroxy-5-iodo-nitrophenyl acetic acid-primed B cells with the production principally of the immunoglobulin G1 (IgG1) and IgM isotypes, small quantities of IgG3, and no detectable IgG2a, or IgG2b. Antigen-specific secretion of IL-2, IL-3, and IL-4 by in vivo effectors was detectable by 12 hours following in vitro restimulation. IFN-gamma and IL-5 were not detected until 48 and 72 hours of culture, respectively, and low levels of these lymphokines were produced. Lymphokine production by primed CD4+ T cells could be induced as early as 3 days following immunization, peaked on day 5, and declined thereafter. The kinetics of in vivo appearance of effector CD4+ T cells that produce lymphokines upon restimulation in vitro were similar for each of the lymphokines examined. Mice depleted of precursor CD4+ T cells by adult thymectomy exhibited limited capacity to generate lymphokine secreting CD4+ T cells in response to primary immunization with KLH, suggesting that the majority of lymphokine producing T cells arise from short-lived and/or precursor cells. Separation of CD4+ T cells from KLH-primed mice on the basis of expression of the lymph node-specific homing receptor, MEL-14, revealed that antigen-specific production of IL-2, IL-3, IL-4, and IFN-gamma was exclusively associated with the MEL-14- subset of CD4+ T cells. Separation on the basis of CD45RB expression, demonstrated that antigen-specific lymphokine production was primarily associated with the minor CD45RB- population, which has been previously associated with memory activity. Our results indicate that primary in vivo immunization leads to the development of a transient population of helper-effectors with a unique phenotype that can produce large quantities of lymphokines and mediate excellent helper activity for B cells.(ABSTRACT TRUNCATED AT 400 WORDS)
Department of Biology, University of California, San Diego, La Jolla 92093-0063.
L M
LM
Bradley
D D
DD
Duncan
S
S
Tonkonogy
S L
SL
Swain
D000818:Animals; D015703:Antigens, CD / Q000032:analysis; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology*; D006433:Hemocyanins / Q000276:immunology; D006649:Histocompatibility Antigens / Q000032:analysis; D007156:Immunologic Memory; D007376:Interleukin-2 / Q000378:metabolism*; D007377:Interleukin-3 / Q000378:metabolism*; D015847:Interleukin-4 / Q000378:metabolism*; D017493:Leukocyte Common Antigens; D008211:Lymphocyte Cooperation; D051379:Mice; D008815:Mice, Inbred Strains; D016201:Receptors, Lymphocyte Homing / Q000032:analysis; D016176:T-Lymphocyte Subsets / Q000276:immunology; D006377:T-Lymphocytes, Helper-Inducer / Q000276:immunology*; D013997:Time Factors
D015703:Antigens, CD; D006649:Histocompatibility Antigens; D007376:Interleukin-2; D007377:Interleukin-3; D016201:Receptors, Lymphocyte Homing; D015847:Interleukin-4; D006433:Hemocyanins; D017493:Leukocyte Common Antigens