title: Evidence implicating I region-restricted antigen presentation in alloantigen and nominal antigen recognition by a dual-reactive helper T lymphocyte clone.
abstract: A helper T lymphocyte clone, designated A10, was generated from spleen cells of a B10.A mouse and demonstrated reactivity to both the nominal protein antigen hen egg ovalbumin (OVA) presented by I-Ak-bearing antigen-presenting cells (APC) and irradiated I-As-bearing spleen cells in the absence of OVA. A stimulatory signal was delivered to the cloned cells by syngeneic spleen cells that were exposed to OVA and then fixed with paraformaldehyde. However, paraformaldehyde-fixed allogeneic spleen cells that bear the I-As determinant recognized by a monoclonal antibody (mAb) were unable, by themselves, to stimulate the A10 cells. The inability of fixed allogeneic spleen cells to stimulate was rectified by the addition of irradiated I-Ak-positive spleen cells, suggesting that at least in this situation, alloantigen must be presented to the alloreactive A10 cells. Further evidence supporting this proposal for class II-restricted presentation of alloantigen included the observations that 1) irradiated I-Ak-negative spleen cells were unable to present the fixed H-2s spleen cells, 2) the anti-I-As mAb blocked the stimulatory signals delivered by irradiated H-2s spleen cells and by fixed H-2s spleen cells plus irradiated syngeneic spleen cells, 3) some anti-I-Ak mAb preparations were able to inhibit stimulation by OVA and by fixed H-2s spleen cells plus irradiated syngeneic spleen cells, and 4) an anti-L3T4a mAb effectively blocked all three stimulatory signals. These data suggested that alloreactivity can be mediated by an antigen-presentation process similar to that proposed for nominal peptide antigen presentation, and that alloantigen in the form of paraformaldehyde-fixed allogeneic spleen cells is recognized in the context of self-determinants before a stimulatory signal can be delivered.
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000502:physiology; D001667:Binding, Competitive; D002999:Clone Cells / Q000276:immunology; D005557:Formaldehyde / Q000494:pharmacology; D006183:H-2 Antigens / Q000276:immunology*; D000949:Histocompatibility Antigens Class II / Q000235:genetics*; D008213:Lymphocyte Activation; D051379:Mice; D008805:Mice, Inbred A; D008810:Mice, Inbred C57BL; D008808:Mice, Inbred CBA; D008811:Mice, Inbred DBA; D010047:Ovalbumin / Q000276:immunology*; D011108:Polymers / Q000494:pharmacology; D013154:Spleen / Q000166:cytology; D006377:T-Lymphocytes, Helper-Inducer / Q000276:immunology*
chemical_list: D000911:Antibodies, Monoclonal; D006183:H-2 Antigens; D000949:Histocompatibility Antigens Class II; D011108:Polymers; D005557:Formaldehyde; D010047:Ovalbumin; C003043:paraform