Antigen presentation by T cells inhibits IL-2 production and induces IL-4 release due to altered cognate signals.
Conflicting results of the effects of Ag presentation by MHC class II-expressing T cells have been described. In some studies class II-expressing T cells have been shown to act as effective APCs, while others have reported that the recognition of Ag on the surface of another T cell inactivates IL-2 production. In this study we have investigated the mechanisms involved in Ag presentation by T cells. The results obtained suggest that 1) lack of costimulation is not responsible for the inhibitory effects of T cell Ag presentation on IL-2 production; the provision of costimulation by immobilized anti-CD28 Ab or by the addition of accessory cells failed to reverse the effects of T cell Ag presentation, but restored the response to immobilized anti-CD3; 2) T cell Ag presentation induced a minimal increase in intracellular Ca2+ compared with that induced by antigen-pulsed B cells; this difference in the calcium response is not explained by quantitative differences in ligand density between B cells and T cells; and 3) despite the weak calcium signal, T cell presentation supported IL-4 release in the absence of IL-2 production. Taken together these data suggest that T cell Ag presentation leads to altered TCR/CD3-transduced signals, which biases the T cell towards a Th2 phenotype.
Lombardi
G
G
Department of Immunology, Royal Postgraduate Medical School, London, United Kingdom.
Hargreaves
R
R
Sidhu
S
S
Imami
N
N
Lightstone
L
L
Fuller-Espie
S
S
Ritter
M
M
Robinson
P
P
Tarnok
A
A
Lechler
R
R
D000818:Animals; D017951:Antigen Presentation / Q000187:drug effects; D000938:Antigen-Presenting Cells / Q000187:drug effects / Q000276:immunology* / Q000378:metabolism; D001402:B-Lymphocytes / Q000276:immunology / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D005110:Extracellular Space / Q000378:metabolism; D006801:Humans; D018664:Interleukin-12 / Q000494:pharmacology; D007376:Interleukin-2 / Q000037:antagonists & inhibitors* / Q000096:biosynthesis* / Q000378:metabolism; D015847:Interleukin-4 / Q000378:metabolism*; D008213:Lymphocyte Activation; D051379:Mice; D015398:Signal Transduction / Q000276:immunology*; D013601:T-Lymphocytes / Q000187:drug effects / Q000276:immunology* / Q000378:metabolism
D007376:Interleukin-2; D018664:Interleukin-12; D015847:Interleukin-4; D002118:Calcium