Table 1.
Characteristics of the adaptive immune system in teleosts and mammals
| Teleosts | Mammals | |
|---|---|---|
| Primary organs | Thymus/head kidney | Thymus/bone marrow |
| Secondary organs | Spleen | Spleen/lymph nodes |
| Mucosa-associated lymphoid tissues |
+ (no Peyer’s Patch) |
+ |
| Germinal centers/FDCs | −a | + |
| B cells | ||
| Immunoglobulins | ||
| Heavy chain (locus configuration) | IgD, IgM, IgT/Zb (translocon)c |
IgD, IgM, IgA, IgG, IgE (translocon) |
| Light chain (locus configuration) | Kappa, lambda, sigma, sigma cart (multi-cluster) |
Kappa/lambda (translocon/multi cluster) |
| Somatic hypermutation | + | + |
| Affinity maturation | Low efficiency | High efficiency |
| Class switch | − | + |
| T cells | ||
| CD4/CD8 subsets | +d | + |
| Th1/Th2/Th17 | + | + |
| TCR αβ/γδ | + | + |
FDCs follicular dendritic cell
a
Putative primordial germinal centers have been characterized
b
In medaka and catfish the IgT/Z has not been identified
c
More than one functional IgH locus in most of studied teleost species
d
Absence of the cd4 and mhc II functional genes in some species (e.g. cod and pipefish)