Table 1.

Distribution of the Immunoglobulin Heavy and Light Chain Isotypes in Vertebrates

	Cartilaginous fishes	Bony fishes	Amphibians	Reptiles	Birds	Mammals
Ig heavy chain	μ, δ, IgNAR	μ, δ, ζ/τ	μ, δ, ν, χ, π$	μ, δ, α, ν	μ, α, ν	μ, δ, α, γ, ε, °*
Ig light chain	σ-cart, σ, κ, λ	σ, κ, λ	σ, κ, λ	κ, λ	λ	κ, λ

^$IgP (ф) isotype is found in newts (Pleurodeles waltl) and is preferentially expressed in the larval stage.

^*IgO (o) isotype is found only in platypus (Ornithorhynchus anatinus).