IgT, a primitive immunoglobulin class specialized in mucosal immunity.
Teleost fish are the most primitive bony vertebrates that contain immunoglobulins. In contrast to mammals and birds, these species are devoid of immunoglobulin A (IgA) or a functional equivalent. This observation suggests that specialization of immunoglobulin isotypes into mucosal and systemic responses took place during tetrapod evolution. Challenging that paradigm, here we show that IgT, an immunoglobulin isotype of unknown function, acts like a mucosal antibody. We detected responses of rainbow trout IgT to an intestinal parasite only in the gut, whereas IgM responses were confined to the serum. IgT coated most intestinal bacteria. As IgT and IgA are phylogenetically distant immunoglobulins, their specialization into mucosal responses probably occurred independently by a process of convergent evolution.
Zhang
Yong-An
YA
Department of Pathobiology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, PA, USA.
Salinas
Irene
I
Li
Jun
J
Parra
David
D
Bjork
Sarah
S
Xu
Zhen
Z
LaPatra
Scott E
SE
Bartholomew
Jerri
J
Sunyer
J Oriol
JO
D000818:Animals; D001402:B-Lymphocytes / Q000166:cytology / Q000276:immunology; D001419:Bacteria / Q000276:immunology; D049109:Cell Proliferation; D004591:Electrophoresis, Polyacrylamide Gel; D018928:Immunity, Mucosal; D007075:Immunoglobulin M / Q000276:immunology; D007136:Immunoglobulins / Q000276:immunology*; D007422:Intestines / Q000276:immunology / Q000382:microbiology / Q000469:parasitology; D009093:Mucus / Q000276:immunology; D055764:Myxozoa / Q000276:immunology; D017686:Oncorhynchus mykiss / Q000145:classification / Q000276:immunology* / Q000382:microbiology / Q000469:parasitology; D010273:Parasitic Diseases, Animal / Q000276:immunology / Q000401:mortality; D010587:Phagocytosis / Q000276:immunology; D010802:Phylogeny
D007075:Immunoglobulin M; D007136:Immunoglobulins