# Developmental changes in the capacity for mucosal immunoglobulin production and secretion in the intestines of growing calves

## TL;DR

This study explores how the ability of calves to produce and secrete mucosal immunoglobulins changes as they grow.

## Contribution

The study reveals the developmental trajectory of mucosal immunoglobulin production and IgA's increasing role in calf intestinal immunity.

## Key findings

- Fecal IgG and IgM levels peak at 1 week but decline sharply, while IgA remains stable and becomes predominant after 4 weeks.
- IgA expression in intestinal mucosa increases with calf growth, supported by upregulated PIGR gene expression.
- Chemokine and receptor levels for plasma cell recruitment do not increase during development.

## Abstract

Neonatal calves predominantly rely on colostral IgG for the passive transfer of immunity; however, little is known about their intrinsic capacity for mucosal immunoglobulin production and the developmental changes associated with their growth. To elucidate the developmental trajectory of mucosal immunity, we investigated changes in mucosal immunoglobulin concentrations and the expression levels of genes involved in immunoglobulin production and secretion across different growth stages in calves. The results demonstrated that fecal IgG and IgM levels exhibited transient peaks at 1 week of age according to smooth spline analysis, followed by sharp decreases, whereas IgA levels remained relatively stable and became the predominant isotype after 4 weeks. Gene expression analysis and immunohistochemistry revealed the localized expression of immunoglobulins in the intestinal mucosa, particularly IgA, which gradually increased with calf growth. The secretion of IgA is also thought to be facilitated by the upregulated expression of PIGR, a gene encoding the IgA transporter whose expression levels increase with calf growth. In contrast, the levels of plasma cell-recruiting chemokines and their receptors were not increased. These results suggest an important role for IgA in the mucosal defense system of the calf intestine, indicating its pivotal function in maintaining gut health following the clearance of colostral IgG.

The online version contains supplementary material available at 10.1186/s13567-025-01648-z.