8536d ch08185-199 8/22/02 12: 12 PM Page 197 mac100 mac 100: 1258 tm: 8536d: Goldsby et al. Immunology 5e Antigen Processing and Presentation CHAPTER8 197 (a) HUMAN CHROMOSOME 1 20 Kb Gene name: CDID CDIA CDIC CDIB CDIE 20 Kb MOUSE CHROMOSOME 3 Gene name: CDIDI CDID2 FICURE8-11 The CDI family of genes and structure of a CD1d ected.()Comparison of the crystal structures of mouse non molecule(a) The genes encoding the CDI family of molecules in classical CD1 and classical class I molecule H-2k. Note the differ human(top)and mouse(bottom). The genes are separated into ences in the antigen binding grooves. (Part(b) reprinted from two groups based on sequence identity; CDIA, B, C, and E are Trends in Immunology (formerly Immunology Today), Vol 19, S.A. group 1, CDID genes are group 2. The products of the pink genes Porcelli and R L. Modlin, The CDI family of lipid antigen presenting have been identified; products of grey genes have not yet been molecules, pp. 362-368, 1998, with permission from Elsevier Science. J with CDla at the surface or in the recycnmal compart- cules on target cae size antigen with class I MHC mole- endocytic CD8 Tc cells reco compartments and CDIb and CDld in the ments. Exactly how the CDI pathway complements or inter- Complexes between antigenic peptides and MHC mole- cules are formed by degradation of a protein antigen in an open question. The T-cell types reactive to CDI were first one of two different antigen-processing pathways thought to be limited to T cells expressing the y8 TCR and lack ing both CD4 and CD8, or T cells with a single TCR a chain, Endogenous antigens are degraded into peptides within but recent reports indicate that a wider range ofT-cell types will the cytosol by proteasomes and assemble with class I mol- recognize CDI-presenting cells Recent evidence indicates that ecules in the rer natural killer T cells recognize CDld molecules presenting au- Exogenous antigens are internalized and degraded within tologous antigen. This may represent a mechanism for elimi- the acidic endocytic compartments and subsequently pair nating cells that are altered by stress, senescence, or neoplasia. with class ll molecules a Peptide binding to class ll molecules involves replacing varian chain in the binding cleft by SUMMARY process catalyzed by nonclassic MHC molecule a T-cells recognize antigen displayed within the cleft of a HLA-DM. If-MHC molecule on the membrane of a cell Presentation of nonpeptide(lipid and glycolipid)anti a In general, CD4 TH cells recognize antigen with class ll gens derived from bacteria involves the class I-like CDl MHC molecules on antigen-processing cells. olecules Gotowww.whfreeman.com/immunology6 Review and quiz of key termswith CD1a at the surface or in the recycling endocytic compartments and CD1b and CD1d in the lysomal compart￾ments. Exactly how the CD1 pathway complements or inter￾sects the better understood class I and class II pathways remains an open question. The T-cell types reactive to CD1 were first thought to be limited to T cells expressing the TCR and lack￾ing both CD4 and CD8, or T cells with a single TCR  chain, but recent reports indicate that a wider range of T-cell types will recognize CD1-presenting cells. Recent evidence indicates that natural killer T cells recognize CD1d molecules presenting au￾tologous antigen. This may represent a mechanism for elimi￾nating cells that are altered by stress, senescence, or neoplasia. SUMMARY ■ T-cells recognize antigen displayed within the cleft of a self-MHC molecule on the membrane of a cell. ■ In general, CD4 TH cells recognize antigen with class II MHC molecules on antigen-processing cells. ■ CD8 TC cells recognize antigen with class I MHC mole￾cules on target cells. ■ Complexes between antigenic peptides and MHC mole￾cules are formed by degradation of a protein antigen in one of two different antigen-processing pathways. ■ Endogenous antigens are degraded into peptides within the cytosol by proteasomes and assemble with class I mol￾ecules in the RER. ■ Exogenous antigens are internalized and degraded within the acidic endocytic compartments and subsequently pair with class II molecules. ■ Peptide binding to class II molecules involves replacing a fragment of invariant chain in the binding cleft by a process catalyzed by nonclassic MHC molecule HLA-DM. ■ Presentation of nonpeptide (lipid and glycolipid) anti￾gens derived from bacteria involves the class I–like CD1 molecules. Antigen Processing and Presentation CHAPTER 8 197 FIGURE 8-11 The CD1 family of genes and structure of a CD1d molecule. (a) The genes encoding the CD1 family of molecules in human (top) and mouse (bottom). The genes are separated into two groups based on sequence identity; CD1A, B, C, and E are group 1, CD1D genes are group 2. The products of the pink genes have been identified; products of grey genes have not yet been detected. (b) Comparison of the crystal structures of mouse non￾classical CD1 and classical class I molecule H-2kb . Note the differ￾ences in the antigen binding grooves. [Part (b) reprinted from Trends in Immunology (formerly Immunology Today), Vol. 19, S. A. Porcelli and R. L. Modlin, The CD1 family of lipid antigen presenting molecules, pp. 362–368, 1998, with permission from Elsevier Science.] HUMAN CHROMOSOME 1 20 Kb Gene name: CD1D CD1E CD1A CD1C CD1B MOUSE CHROMOSOME 3 20 Kb Gene name: CD1D1 CD1D2 (a) Go to www.whfreeman.com/immunology Self-Test Review and quiz of key terms 8536d_ch08_185-199 8/22/02 12:12 PM Page 197 mac100 mac 100: 1268_tm:8536d:Goldsby et al. / Immunology 5e-: