Impact of aging on distribution of IgA+ and IgG+ cells in aggregated lymphoid nodules area in abomasum of Bactrian camels (Camelus bactrianus)

The aggregated lymphoid nodules area (ALNA) in the abomasum is a special organized lymphoid tissue discovered only in Bactrian camels at present. This study aimed to explore the impact of aging on distribution of IgA+ and IgG+ cells in ALNA in abomasum of Bactrian camels. Twenty-four Alashan Bactrian camels were divided into the following four age groups: young (1-2 years), pubertal (3-5 years), middle-aged (6-16 years) and old (17-20 years). IgA+ and IgG+ cells in the lamina propria of ALNA were observed and analyzed using immunohistochemical and statistical techniques. The results showed that, in ALNA, the distribution of IgA+ and IgG+ cells were diffuse, and only a few were in subepithelium dome (SED) and most of them in non-SED. Meanwhile, there were significantly more IgA+ cells than IgG+ cells in SED from the young to the middle aged group, but which reversed in old group (P < 0.05). However, the aging significantly decreased the densities of IgA+ and IgG+ cells populations in non-SED (P < 0.05); in SED, there were no significant differences between the densities of IgA+ and IgG+ cells, but which were both significantly lower in old group than those in young group (P < 0.05). The results demonstrated that, in mucosal effector sites, the aging significantly decreased the densities of IgA+ and IgG+ cells populations and impacted on the defense barriers formed by IgA and IgG, but had no impact on the scattered characteristics. In inductive sites, the aging dramatically declined their densities, and they should have close relationships with immune memory. These findings lay the foundation for further researching the mucosal immune disorder or decline caused by aging, and especially underscore the importance of researching the impact of aging on the relationship between IgA+ and IgG+ cells populations and the microbiota colonized in abomasum of Bactrian camels.