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Antigen is required for the activation of effector activities, whereas interleukin 2 Is required for the maintenance of memory in ovalbumin-specific, CD8+ cytotoxic T lymphocytes.

Ke Y, Ma H, Kapp JA - J. Exp. Med. (1998)

Bottom Line: Thus, the effector functions of these CTLs were rapidly induced by T cell receptor (TCR) occupancy.In the absence of OVA, the precursor frequency was identical in spleens of normal and beta2-microglobulin knockout recipients, but significantly less in IL-2 knockout mice.The decline of memory in the absence of IL-2 supports data from other investigators, suggesting that cell cycling is important to the maintenance of CD8+ T cell memory.

View Article: PubMed Central - PubMed

Affiliation: Department of Ophthalmology, Emory University School of Medicine, Atlanta, GA 30322, USA.

ABSTRACT
The mechanisms that maintain memory in T cells are not completely understood. We have investigated the role of antigen and interleukin (IL)-2 in the growth and maintenance of CD8+ T cells using a cytolytic T cell line specific for ovalbumin (OVA)257-264 presented by H-2Kb. This line does not secrete IL-4 or IL-2; hence, stimulation with the OVA-transfected EL4 line (E.G7-OVA) does not induce proliferation without addition of exogenous growth factors. Furthermore, this line can be maintained continuously by weekly addition of irradiated, splenic filler cells and IL-2, with or without E.G7-OVA. Although IL-2 induced proliferation of these cytotoxic T lymphocytes (CTLs), production of interferon gamma and tumor necrosis factor alpha required stimulation of the CTL with E. G7-OVA. The kinetics of lymphokine secretion after stimulation by E. G7-OVA were the same whether the CTL had been maintained with or without antigen (Ag). In addition, both CTL lines killed E.G7-OVA target cells within 4 h. Thus, the effector functions of these CTLs were rapidly induced by T cell receptor (TCR) occupancy. CTLs cultured with or without Ag also served as memory T cells when parked for 100 d in unirradiated, syngeneic recipients without OVA. In the absence of OVA, the precursor frequency was identical in spleens of normal and beta2-microglobulin knockout recipients, but significantly less in IL-2 knockout mice. The decline of memory in the absence of IL-2 supports data from other investigators, suggesting that cell cycling is important to the maintenance of CD8+ T cell memory. These data also suggest that stimulation of OVA-specific CTLs by lymphokines seems to be more important to maintaining memory than stimulation of TCRs by cross-reactive peptides complexed to class I molecules.

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Comparison of cytolytic activity between stimulated and unstimulated CTLs. Stimulated OVA-CTLs were stimulated weekly with  irradiated E.G7-OVA, syngeneic filler cells, and Con A supernatant. Unstimulated OVA-CTLs were maintained by weekly replenishment with  irradiated filler cells and Con A supernatant, but without E.G7-OVA. After (A) 50 or (B) 100 d, stimulated and unstimulated OVA-CTLs cultured  with IL-2 (triangles) or E.G7-OVA plus IL-2 (circles) were tested for cytolytic activity using 51Cr-labeled EL4 and E.G7-OVA targets at various  E/T ratios. After incubation at 37°C for 4 h, supernatants were harvested  and radioactivity was counted. The results are the mean of triplicates ±  SD from a representative experiment repeated several times with similar  results.
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Figure 3: Comparison of cytolytic activity between stimulated and unstimulated CTLs. Stimulated OVA-CTLs were stimulated weekly with irradiated E.G7-OVA, syngeneic filler cells, and Con A supernatant. Unstimulated OVA-CTLs were maintained by weekly replenishment with irradiated filler cells and Con A supernatant, but without E.G7-OVA. After (A) 50 or (B) 100 d, stimulated and unstimulated OVA-CTLs cultured with IL-2 (triangles) or E.G7-OVA plus IL-2 (circles) were tested for cytolytic activity using 51Cr-labeled EL4 and E.G7-OVA targets at various E/T ratios. After incubation at 37°C for 4 h, supernatants were harvested and radioactivity was counted. The results are the mean of triplicates ± SD from a representative experiment repeated several times with similar results.

Mentions: Based on the observation that IL-2 was sufficient for maintaining CTL growth in short-term cultures, we grew the OVA-CTLs by repeated stimulation with filler cells and IL-2, but without E.G7-OVA. After culturing for 50 and 100 d, the cytolytic activity of these unstimulated OVA-CTLs was tested. No significant difference in cytolytic activity of OVA-CTLs maintained without antigen was observed by comparison to OVA-CTLs that were restimulated weekly with E.G7-OVA (Fig. 3). The specificity of the CTL was maintained as shown by killing of E.G7-OVA but not EL4 targets. These data suggest that Ag is not required to maintain T cell memory in vitro.


Antigen is required for the activation of effector activities, whereas interleukin 2 Is required for the maintenance of memory in ovalbumin-specific, CD8+ cytotoxic T lymphocytes.

Ke Y, Ma H, Kapp JA - J. Exp. Med. (1998)

Comparison of cytolytic activity between stimulated and unstimulated CTLs. Stimulated OVA-CTLs were stimulated weekly with  irradiated E.G7-OVA, syngeneic filler cells, and Con A supernatant. Unstimulated OVA-CTLs were maintained by weekly replenishment with  irradiated filler cells and Con A supernatant, but without E.G7-OVA. After (A) 50 or (B) 100 d, stimulated and unstimulated OVA-CTLs cultured  with IL-2 (triangles) or E.G7-OVA plus IL-2 (circles) were tested for cytolytic activity using 51Cr-labeled EL4 and E.G7-OVA targets at various  E/T ratios. After incubation at 37°C for 4 h, supernatants were harvested  and radioactivity was counted. The results are the mean of triplicates ±  SD from a representative experiment repeated several times with similar  results.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2199192&req=5

Figure 3: Comparison of cytolytic activity between stimulated and unstimulated CTLs. Stimulated OVA-CTLs were stimulated weekly with irradiated E.G7-OVA, syngeneic filler cells, and Con A supernatant. Unstimulated OVA-CTLs were maintained by weekly replenishment with irradiated filler cells and Con A supernatant, but without E.G7-OVA. After (A) 50 or (B) 100 d, stimulated and unstimulated OVA-CTLs cultured with IL-2 (triangles) or E.G7-OVA plus IL-2 (circles) were tested for cytolytic activity using 51Cr-labeled EL4 and E.G7-OVA targets at various E/T ratios. After incubation at 37°C for 4 h, supernatants were harvested and radioactivity was counted. The results are the mean of triplicates ± SD from a representative experiment repeated several times with similar results.
Mentions: Based on the observation that IL-2 was sufficient for maintaining CTL growth in short-term cultures, we grew the OVA-CTLs by repeated stimulation with filler cells and IL-2, but without E.G7-OVA. After culturing for 50 and 100 d, the cytolytic activity of these unstimulated OVA-CTLs was tested. No significant difference in cytolytic activity of OVA-CTLs maintained without antigen was observed by comparison to OVA-CTLs that were restimulated weekly with E.G7-OVA (Fig. 3). The specificity of the CTL was maintained as shown by killing of E.G7-OVA but not EL4 targets. These data suggest that Ag is not required to maintain T cell memory in vitro.

Bottom Line: Thus, the effector functions of these CTLs were rapidly induced by T cell receptor (TCR) occupancy.In the absence of OVA, the precursor frequency was identical in spleens of normal and beta2-microglobulin knockout recipients, but significantly less in IL-2 knockout mice.The decline of memory in the absence of IL-2 supports data from other investigators, suggesting that cell cycling is important to the maintenance of CD8+ T cell memory.

View Article: PubMed Central - PubMed

Affiliation: Department of Ophthalmology, Emory University School of Medicine, Atlanta, GA 30322, USA.

ABSTRACT
The mechanisms that maintain memory in T cells are not completely understood. We have investigated the role of antigen and interleukin (IL)-2 in the growth and maintenance of CD8+ T cells using a cytolytic T cell line specific for ovalbumin (OVA)257-264 presented by H-2Kb. This line does not secrete IL-4 or IL-2; hence, stimulation with the OVA-transfected EL4 line (E.G7-OVA) does not induce proliferation without addition of exogenous growth factors. Furthermore, this line can be maintained continuously by weekly addition of irradiated, splenic filler cells and IL-2, with or without E.G7-OVA. Although IL-2 induced proliferation of these cytotoxic T lymphocytes (CTLs), production of interferon gamma and tumor necrosis factor alpha required stimulation of the CTL with E. G7-OVA. The kinetics of lymphokine secretion after stimulation by E. G7-OVA were the same whether the CTL had been maintained with or without antigen (Ag). In addition, both CTL lines killed E.G7-OVA target cells within 4 h. Thus, the effector functions of these CTLs were rapidly induced by T cell receptor (TCR) occupancy. CTLs cultured with or without Ag also served as memory T cells when parked for 100 d in unirradiated, syngeneic recipients without OVA. In the absence of OVA, the precursor frequency was identical in spleens of normal and beta2-microglobulin knockout recipients, but significantly less in IL-2 knockout mice. The decline of memory in the absence of IL-2 supports data from other investigators, suggesting that cell cycling is important to the maintenance of CD8+ T cell memory. These data also suggest that stimulation of OVA-specific CTLs by lymphokines seems to be more important to maintaining memory than stimulation of TCRs by cross-reactive peptides complexed to class I molecules.

Show MeSH
Related in: MedlinePlus