Cholera toxin increases intracellular pH in B lymphoma cells and decreases their antigen-presenting ability

Abstract

Cholera toxin (CT) can function as a potent adjuvant in the mucosal immune response. However, we have found that treatment of A20-HL murine B lymphoma cells with CT severely inhibits the presentation of ovalbumin (OVA) to cells of the T cell clone 42-6A specific for OVA 323-339 /I-A d , whereas it does not affect the presentation of OVA 323-339 peptide. CT treatment did not affect the expression of B7-1, B7-2, ICAM-1, LFA-1 or MHC class II on, or the internalization of OVA into A20-HL cells. In CT-treated A20-HL cells, degradation of OVA was decreased, and intracellular pH was raised to a level approximately equivalent to that in CH 3 NH 2 -treated cells. Treatment with CH 3 NH 2 is known to raise the pH in endocytic structures and thus inhibits antigen processing. Treatment of A20-HL cells with dibutyryl-cAMP similarly increased intracellular pH. The increase in intracellular pH following CT treatment was inhibited by a cAMP inhibitor, 2',3'-dideoxyadenosine. These results strongly suggest that CT treatment of A20-HL cells inhibits their antigen-presenting cell function by triggering the cAMP cascade, increasing intracellular pH, and reducing the degradation of OVA.

Modulation of Innate and Acquired Immune Responses by Escherichia coli Heat-Labile Toxin: Distinct Pro- and Anti-Inflammatory Effects of the Nontoxic AB Complex and the Enzyme Activity

“…A role for the enzyme activity in inhibiting APC function is consistent with a report that LT and CT could inhibit the functions of APC by inhibiting intracellular Ag processing in a manner dependent on ADP-ribosyltransferase (31). The treatment of B lymphoma cells with CT was also found to inhibit their APC function by triggering the cAMP cascade, resulting in increased intracellular pH and reduction of the degradation of Ag (32). The enhancement of Th2 cytokine production, which appears to be independent of enzyme activity, may also operate through a nonspecific mitogenic effect of LT on Th2 cells, analogous to the effect of PT on Th1 cells (24).…”

Selective enhancement of B cell antigen receptor‐mediated antigen presentation by treatment with transforming growth factor‐β

“…Rat anti-Lamp-1 mAb (1D4B) was obtained from Pharmingen, San Diego, CA, USA. OVA 323-339 peptide was synthesized as described previously [41], and kindly provided by Dr S. Imajoh-Ohmi, Institute of Medical Science, University of Tokyo, Tokyo, Japan. TNP 3.9 -OVA and FITC-conjugated OVA or TNP 3.9 -OVA were prepared as described previously [24,42].…”

“…l culture medium on a 96-well culture plate. In some experiments A20-HL cells treated or untreated with TGF-g 1 were pulsed with Ag and fixed with paraformaldehyde as described previously [41]. When Ag-pulsed and fixed A20-HL cells were used as APC, 2.5×10 5 fixed A20-HL cells were incubated with 4×10 4 42-6A cells.…”