MHC class I presentation of live and heat-inactivated Sendai virus antigen in T2Kb cells depends on an intracellular compartment with endosomal characteristics.

T2Kb cells, which do not express TAP1/2 peptide transporters or the low molecular weight protein 2/7 (LMP2/7) proteasomal subunits, can still process and present both live and heat-inactivated Sendai virus (SV). As this operation may also reflect the existence of an alternative processing pathway in normal antigen-presenting cells (APC), the authors have characterized it using intracellular inhibitors and anti-Kb monoclonal antibodies (MoAbs). From the results with lipophilic amines (ammonium chloride, methylamine and chloroquine), cytoskeletal inhibitors (cytochalasin B and vinblastine), and an endoprotease inhibitor (phenylmethylsulfonyl fluoride, PMSF), the authors conclude that the processing of SV antigen in T2Kb cells has endosomal characteristics depending on cellular activities such as uptake, vesicular transport and intracellular-vesicular proteolysis. In addition, internalized 'empty' Kb molecules derived from the T2Kb cell surface appeared to be involved in the presentation of SV antigen, as demonstrated by a protocol using a combination of the Golgi inhibitor brefeldin A(BFA) and anti-Kb antibodies. The results thus indicate that T2Kb cells process SV antigen in an endosomal-like compartment which contain recycling 'empty' Kb molecules.