Analysis of class II MHC structure in thymic nurse cells.
During the course of thymocyte maturation, the processes of positive selection and tolerance induction are mediated by interactions between thymocyte T-cell receptors and MHC molecules on thymic stromal cells. The means by which these seemingly contrary processes can be mediated by interactions between the same molecules has long been a source of controversy. One idea which has been put forward is that the MHC molecules in different microenvironments of the thymus are not the same. We have tested this hypothesis by examining class II transcripts derived from thymic cortical epithelial cells known as thymic nurse cells, reasoning that alternative splicing of primary transcripts might give rise to a positively selecting MHC molecule. However, we found no evidence for alternative splicing of these transcripts. These results are presented and discussed with regard to implications for possible mechanisms of positive selection.
Howard Hughes Medical Institute, National Jewish Center for Immunology and Respiratory Medicine, Denver, Colorado 80206.
J E
JE
McCormack
T
T
Wade
H
H
Morales
J
J
Kappler
P
P
Marrack
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D000949:Histocompatibility Antigens Class II / Q000737:chemistry* / Q000502:physiology; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D012326:RNA Splicing; D012333:RNA, Messenger / Q000032:analysis; D011948:Receptors, Antigen, T-Cell / Q000502:physiology; D013950:Thymus Gland / Q000276:immunology*
D000949:Histocompatibility Antigens Class II; D012333:RNA, Messenger; D011948:Receptors, Antigen, T-Cell