Data from: The genetic architecture of helminth-specific immune responses in a wild population of Soay sheep (Ovis aries)

Much of our knowledge of the drivers of immune variation, and how these
responses vary over time, comes from humans, domesticated livestock or
laboratory organisms. While the genetic basis of variation in immune
responses have been investigated in these systems, there is a poor
understanding of how genetic variation influences immunity in natural,
untreated populations living in complex environments. Here, we examine the
genetic architecture of variation in immune traits in the Soay sheep of St
Kilda, an unmanaged population of sheep infected with strongyle
gastrointestinal nematodes. We assayed IgA, IgE and IgG antibodies against
the prevalent nematode Teladorsagia circumcincta in the blood plasma of
> 3,000 sheep collected over 26 years. Antibody levels were
significantly heritable (h2 = 0.21 to 0.57) and highly stable over an
individual’s lifespan. IgA levels were strongly associated with a region
on chromosome 24 explaining 21.1% and 24.5% of heritable variation in
lambs and adults, respectively. This region was adjacent to two candidate
loci, Class II Major Histocompatibility Complex Transactivator (CIITA) and
C-Type Lectin Domain Containing 16A (CLEC16A). Lamb IgA levels were also
associated with the immunoglobulin heavy constant loci (IGH) complex, and
adult IgE levels and lamb IgA and IgG levels were associated with the
major histocompatibility complex (MHC). This study provides evidence of
high heritability of a complex immunological trait under natural
conditions and provides the first evidence from a genome-wide study that
large effect genes located outside the MHC region exist for immune traits
in the wild.