Table 1.
Innate and adaptive immune systems in bats and birds
| Protein | Function | Bats | Birds | |
|---|---|---|---|---|
| Innate immunity | RIG-I | Cytosolic PRR; detects dsRNA | Present and functional in the black flying fox (Pteropus alecto; AEW46678); homolog also present in David's Myotis (Myotis davidii; ELK34300) [16] | Present and functional in mallard duck (ACA61272) and present in goose (ADV58759), but absent in chicken [33] |
| MDA5 | Cytosolic PRR; detects dsRNA | Present and functional in black flying fox (P. alecto; AEW46679); homolog also present in David's Myotis (M. davidii; ELK28159) | Present in mallard duck (GU936632), goose (AGC51036), and chicken (ADD83027) 33, 86 | |
| LGP2 | Cytosolic PRR; detects dsRNA | Present and functional in black flying fox (P. alecto); homolog also present in David's Myotis (M. davidii) | Present in chicken [34] | |
| TLR7 | Membrane-bound PRR; detects ssRNA | Present in black flying fox (P. alecto; ADO01609), Leschenault's rousette (Rousettus leschenaultia; BAH02556), and David's Myotis (M. davidii; ELK30184) 15, 85 | Present in chicken (ACR26250) and mallard duck (ABK51522) 35, 87, 88 | |
| TLR3 | Membrane-bound PRR; detects dsRNA | Present in black flying fox (P. alecto; ADO01605), Leschenault's rousette (R. leschenaultia; BAH02555), and David's Myotis (M. davidii; ELK23529) 15, 85 | Present in chicken (ABG79022) and muscovy duck (AFK29094) [89] | |
| TLR8 | Membrane-bound PRR; detects ssRNA | Present in black flying fox (P. alecto; ELK17709) and David's Myotis (M. davidii; ELK30183) [85] | Disrupted in chicken and duck genome [90] | |
| IFN-α | Type I IFN; inducible cytokine that regulates the antiviral response | Variable number of members present in multiple bat species, including black flying fox (P. alecto; α1: ELK15818, α5: ELK06973) and David's Myotis (M. davidii; α3: ELK29335); may be absent in other Myotis sp. [17] | At least 13 putative IFN-α genes identified in the chicken genome [91]; also identified in the mallard duck (ADU60335) and Gerylag goose (AFU54612), but exact number of members is not known | |
| IFN-β | Type I IFN; inducible cytokine that regulates the antiviral response | Present in multiple bat species, including black flying fox (P. alecto; ELK06976) and David's Myotis (M. davidii; ELK29334) | Present in chicken (NP_001020007) and mallard duck | |
| IFN-ω | Type I IFN; inducible cytokine that regulates the antiviral response | Multiple members present in bats, including black flying fox (P. alecto; ELK06971, ELK06975, ELK08131, ELK15817, and ELK15819) and David's Myotis (M. davidii; ELK26494, ELK26493, and ELK26495) | Absent | |
| IFN-λ | Type III IFN; inducible cytokine that regulates the antiviral response | Two members identified in black flying fox (P. alecto; λ1: AEF33950, λ2: AEF33949); also present in the closely related Malaysian flying fox (Pteropus vampyrus) [18] | At least one member present in chicken (ABU82742) [92] | |
| Adaptive immunity | Ig VH | Variable region of immunoglobulin heavy chain; contributes to diversity of antibody repertoire | At least 23 genes classified into five families were identified in the black flying fox (P. alecto; GQ427153:GQ427172) [18]; diverse genes in the VH3 family repertoire also reported for other bat species [93] | Single functional VH gene in chicken; 58 ψVH pseudogenes located upstream in IgH locus also contribute to repertoire diversity through gene conversion; similar organization in ducks and other birds [37] |
| Ig DH | Diversity region of Ig heavy chain; contributes to diversity of antibody repertoire | Diverse DH elements in the little brown bat (Myotis lucifugus) [93] | Approximately 15 DH elements in chicken | |
| Ig JH | Joining region of Ig heavy chain | At least 13 elements identified in the little brown bat (M. lucifugus) [93] | Single JH element in chicken | |
| Ig VL | Variable region of immunoglobulin light chain; contributes to diversity of antibody repertoire | λ and κ loci present in black flying fox (P. alecto) [94], representative of megabats; λ locus present in microbats, but κ locus is absent [94] | Single functional VL gene in single (λ) IgL locus in chicken; approximately 25 ψVL pseudogenes contribute through gene conversion [95] | |
| Ig JL | Joining region of Ig light chain | (Not studied) | Single JL element in chicken | |
| Ig Cδ | Constant region of IgD | Absent in black flying fox (P. alecto) and probably other megabats; present in microbats, such as the little brown bat (Myotis lucifugus; ADI96045, ADI96044) [96] | Absent |