Data from: Vitally important – does early innate immunity predict recruitment and adult innate immunity?

The immune system is one of the most important adaptations that has
evolved to protect animals from a wide range of pathogens they encounter
from early life onwards. During the early developmental period this is
particularly true for the innate immunity, as other components of the
immune system are, as yet, poorly developed. But innate immunity may not
only be crucial for early life survival, but may also have long-lasting
effects, for example if early life immunity reflects the functioning of
the immune system as a whole. For this reason, we investigated the
importance of four constitutive innate immune parameters (natural
antibodies, complement activity, concentrations of haptoglobin, and
concentrations of nitric oxide) for recruitment in free-living great tits.
We compared nestling immunity of recruits with nestling immunity of their
nonrecruited siblings. We also investigated within individual consistency
of these innate immune parameters for those individuals that recruited,
which may be taken as a measure of immune capacity. In accordance with
previous studies, we found a clear effect of tarsus length and a trend for
body mass on the likelihood to recruit. Nevertheless, we found no evidence
that higher levels of constitutive innate immunity as a nestling
facilitated local recruitment. Furthermore, individual innate immunity was
not consistent across life stages, that is to say, nestling immune
parameters did not determine, or respectively, reflect adult innate immune
parameters. This plasticity in innate immune components may explain why we
did not find long-lasting survival benefits.

免疫系统是演化形成的最重要适应性机制之一，可保护动物自生命早期起便免受其所接触的各类病原体的侵害。在发育早期，先天免疫（innate immunity）的作用尤为关键，因为此时免疫系统的其他组分尚未发育完全。然而，先天免疫不仅对生命早期的存活至关重要，还可能产生长期影响——例如，若生命早期的免疫状态能够反映整个免疫系统的整体功能时。
基于此，我们针对自由生活的大山雀（great tits）的种群招募过程，探究了四项组成型先天免疫参数的重要性：天然抗体（natural antibodies）、补体活性（complement activity）、触珠蛋白（haptoglobin）浓度以及一氧化氮（nitric oxide）浓度。我们将成功招募的幼鸟的免疫指标，与其未成功招募的同胞幼鸟的免疫指标进行了对比。此外，我们还针对成功招募的个体，探究了这些先天免疫参数的个体内一致性，该指标可被用作免疫能力（immune capacity）的衡量标准。
与既往研究结果一致，我们发现跗跖长度（tarsus length）对招募成功率存在显著影响，而体质量（body mass）则呈现出潜在的影响趋势。然而，我们并未发现证据表明，雏鸟时期更高的组成型先天免疫水平能够提升局部招募的概率。此外，个体的先天免疫状态在不同生命阶段间并不具有一致性，换言之，雏鸟时期的免疫参数既无法决定，也无法反映成体的先天免疫参数。先天免疫组分的这种可塑性，或可解释我们为何未发现长期的生存益处。