Biology ETDs
Publication Date
Spring 5-16-2026
Abstract
The mucosal immune system is vital to protecting organisms from pathogen invasion. Organized structures within the mucosal immune system drive much of the adaptive immune responses to pathogens and the microbiota. In mammals, the organization of the immune system is vital to its function: without lymph nodes, germinal centers, or lymphotoxin alpha, the key factor driving the development of many of these structures, the immune system is severely weakened. Fish lack both lymph nodes and lymphotoxin alpha, yet they manage to produce effective antibody responses, albeit with lower levels of affinity maturation. We have found an organized structure that closely resembles a mammalian germinal center, the organized nasopharynx-associated lymphoid tissue (O-NALT) in the nasal cavity of at least two species of teleost fish, rainbow trout and zebrafish. This structure is found in the lymphoepithelium lining the nasal cavity and appears as an intraepithelial “bulge” packed with IgM+ B cells, CD4-2+ T cells, nestled in a network of fibroblastic reticular cells. The O-NALT expands in response to vaccination, with increased expression of aicda, the enzyme responsible for somatic hypermutation, as well as increased levels of B cell proliferation and apoptosis, all hallmarks of a germinal center-like structure. Developmentally, the O-NALT is seeded by cells in the same trajectory to that seen in mammalian NALT, beginning with CD8+ T cells, followed by IgM+ B cells and CD4+ T cells, and in rainbow trout development is completed by 1400 degree days. The O-NALT is surrounded by two populations of MHC-II+ cells, one nestled within the fibroblastic reticular cells, with the other found underneath the basement membrane of the O-NALT. Curiously, antigen uptake seems to occur most rapidly in a structure near the O-NALT, the olfactory rosette, but antigen is retained for up to 2 weeks in the O-NALT, not in the rosette. When exposed to antigens in a prime-boost experiment, fish seeing protein antigens for the first time took it up at higher levels than those exposed to antigen two weeks prior to administration, indicating that antigen uptake patterns do not follow those observed in mammalian models. Taken together, these findings indicate that the O-NALT has many traits resembling mammalian NALT, both in response to vaccination and developmental seeding patterns, but also shows many unique responses to repeated antigen exposure that need to be studied further.
Language
English
Document Type
Dissertation
Degree Name
Biology
Level of Degree
Doctoral
Department Name
UNM Biology Department
First Committee Member (Chair)
Irene Salinas
Second Committee Member
Robert D. Miller
Third Committee Member
Russel Morton
Fourth Committee Member
David Tobin
Recommended Citation
Garcia, Benjamin J.. "Organization and development of nasal immunity in teleosts." (2026). https://digitalrepository.unm.edu/biol_etds/660