Laura A. Vogel

Purpose: The purpose of this study was to introduce a native labral variant, the everted acetabular labrum, and to describe the patho‐anatomy, magnetic resonance imaging and magnetic resonance arthrogram (MRI/MRA) characteristics and the arthroscopic findings in this condition. Methods: All primary hip arthroscopy procedures performed by the senior author between June 2013 and January 2020 were reviewed retrospectively. An everted acetabular labrum was identified as a segment of labrum that lacked apposition to the femoral head with the hip off traction. All everted labra were treated with labral advancement and repair with or without augmentation or reconstruction. The labrum‐to‐femoral head distance was measured in 3T MRI/MRA at the 1‐2 o’clock position. A random selection of 38 hips without an everted labrum served as controls to compare radiographic parameters. Results: A total of 68 hips were identified as having an everted labrum during the study period (mean age, 29.1 years), and 55 hips had advanced imaging available for review. MRI/MRA scans revealed the everted labrum to have a triangular shape in 17 hips (31%) and a blunted/round shape in 38 hips (69%), which differed significantly from controls (triangular 25/38 [66%], blunted 13/38 [34%], P < 0.001). The average labrum‐to‐femoral head distance was 1.4 mm for everted labra versus 0.0 mm for controls ( P < 0.0001) and the mean labral lengths and widths were significantly shorter than those of controls (both P < 0.01). Of the hips, 8 underwent labral reconstruction or augmentation, and 61 underwent labral advancement/repair. Conclusion: The everted acetabular labrum is a native variant that is identifiable during hip arthroscopy by assessing the labral seal off traction. Preoperative MRI/MRA findings can be highly predictive of an everted labrum. Surgical treatment includes labral advancement and repair or reconstruction to restore contact between the labrum and the femoral head. Level of Evidence: III, retrospective comparative study.

Disease is a significant threat in the global decline of reptile species. Many aquatic reptiles live in habitats with high levels of opportunistic microbial pathogens, yet little is known about their immune system. Gut‐associated lymphoid tissue is vital for protection against ingested pathogens and maintenance of normal gut microbiota. In mammals, gut mucosal immunity is well‐characterized and mucosal surfaces are coated in protective antibodies. However, reptiles lack lymph nodes and Peyer's patches, which are the major sites of mammalian B cell responses. The presence or distribution of mucosal B cells in reptiles is unknown. In this study, we first set out to determine if B cells could be detected in intestinal tissues of red‐eared slider turtles, Trachemys scripta. Using whole‐mount immunochemistry and a primary antibody to turtle antibody light chains, we identified widely distributed B cell aggregates within the small intestine of hatchling turtles. These aggregates appeared similar to isolated lymphoid follicles (ILFs) in mammals and the frequency was much higher in distal intestinal sections than in proximal sections. To determine if these structures were inducible in the presence of microbes, we introduced an enteric Salmonella species through oral gavage. Analysis of intestinal tissues revealed that hatchlings exposed to Salmonella exhibited significantly more of these aggregates when compared with those that did not receive bacteria. These studies provide the first evidence for B cell‐containing ILF‐like structures in reptiles and provide novel information about gut immunity in nonmammalian vertebrates that could have important implications for ecological interactions with pathogens.

Summary: Temperature affects nearly all aspects of the physiology of ectotherms, including their ability to mount an immune response. Typically, the ectothermic vertebrate immune system can respond over a wide range of temperatures, but there is a species‐specific temperature at which responses are strongest, with impaired responses above and below this threshold. In long‐lived ectotherms, ageing could also influence the ability to respond to temperature changes as immunosenecence, the functional decrease in immune function with age, is widely reported. This study examined the effects of the interaction between temperature and age on B‐cell function in a long‐lived reptile, the red‐eared slider turtle, Trachemys scripta. B cells in this species have previously been shown to have two main functions, phagocytosis and antibody production. Adult turtles were trapped and blood samples taken. Because sliders grow throughout their lifetime, plastron length was used as a proxy for age. Leucocytes were isolated and used in either an ELISpot assay to examine their ability to produce antibodies spontaneously or when stimulated, or used in a phagocytic assay. The ELISpot and phagocytic assays were conducted over a range of biologically relevant temperatures. We found no interaction between age and temperature on any measure of B‐cell function. In all cases there was a significant effect of temperature, with impaired function at temperatures below 29 °C, but no impairment of function at higher temperatures. We also found little evidence of immunosenescence in any response. This study provides insight into the thermal biology of B‐cell function in sliders and provides an interesting connection between immunology, behaviour and ecology in this long‐lived turtle. A lay summary is available for this article.

Life-history studies of wild bird populations often focus on the relationship between an individual’s condition and its capacity to mount an immune response, as measured by a commonly-employed assay of cutaneous immunity, the PHA skin test. In addition, haematocrit, the packed cell volume in relation to total blood volume, is often measured as an indicator of physiological performance. A multi-year study of a wild population of house wrens has recently revealed that those exhibiting the highest condition and strongest PHA responses as nestlings are most likely to be recruited to the breeding population and to breed through two years of age; in contrast, intermediate haematocrit values result in the highest recruitment to the population. Selection theory would predict, therefore, that most of the underlying genetic variation in these traits should be exhausted resulting in low heritability, although such traits may also exhibit low heritability because of increased residual variance. Here, we examine the genetic and environmental variation in condition, cutaneous immunity, and haematocrit using an animal model based on a pedigree of approximately 2,800 house wrens. Environmental effects played a paramount role in shaping the expression of the fitness-related traits measured in this wild population, but two of them, condition and haematocrit, retained significant heritable variation. Condition was also positively correlated with both the PHA response and haematocrit, but in the absence of any significant genetic correlations, it appears that this covariance arises through parallel effects of the environment acting on this suite of traits. The maintenance of genetic variation in different measures of condition appears to be a pervasive feature of wild bird populations, in contradiction of conventional selection theory. A major challenge in future studies will be to explain how such variation persists in the face of the directional selection acting on condition in house wrens and other species.

Measures of body condition, immune function, and hematological health are widely used in ecological studies of vertebrate populations, predicated on the assumption that these traits are linked to fitness. However, compelling evidence that these traits actually predict long‐term survival and reproductive success among individuals in the wild is lacking. Here, we show that body condition (i.e., size‐adjusted body mass) and cutaneous immune responsiveness to phytohemagglutinin (PHA) injection among neonates positively predict recruitment and subsequent longevity in a wild, migratory population of House Wrens (Troglodytes aedon). However, neonates with intermediate hematocrit had the highest recruitment and longevity. Neonates with the highest PHA responsiveness and intermediate hematocrit prior to independence eventually produced the most offspring during their lifetime breeding on the study site. Importantly, the effects of PHA responsiveness and hematocrit were revealed while controlling for variation in body condition, sex, and environmental variation. Thus, our data demonstrate that body condition, cutaneous immune responsiveness, and hematocrit as a neonate are associated with individual fitness. Although hematocrit's effect is more complex than traditionally thought, our results suggest a previously underappreciated role for this trait in influencing survival in the wild.

Summary: The field of eco‐immunology seeks to address the causes and consequences of natural variation in immune responses. Recently, the development of more immunological resources for nonmodel systems along with the growing availability of genomic data has made it feasible to explore more complex immunological differences in nonmodel systems. Cytokines are small molecular weight proteins that are the major signalling molecules of the immune system. Studies in mice and humans have demonstrated the importance of tightly regulated cytokine signalling, and thus, cytokines may play a major, unexplored role in explaining natural variation in immune responses. In this review, we highlight cytokines that are likely to be important for eco‐immunology studies and what is currently known about their presence or absence in the major vertebrate groups. We also explore what types of questions an eco‐immunologist might ask involving cytokines and discuss potential ways to measure cytokines in nonmodel systems. Inclusion of cytokines in eco‐immunology will advance the field as it will help us to better understand mechanisms behind both natural variation in immune responses and how different taxa respond to immune challenges.