Between breed comparisons of eosinophil level
Altered patterns of eosinophil regulation were identified across different tick life stages and will hence be discussed accordingly. Three conclusions can be drawn regarding the attachment of larvae on cattle. Firstly, upon tick larvae attachment, there was an overall increase in the number of eosinophils at the site of tick attachment in all cattle breeds. Susceptible cattle did, however, display a higher influx of eosinophils compared to their tick-resistant counterparts (Figure 1.1; Moorhouse and Tatchell, 1969; Piper et al., 2010; Franzin et al., 2017). Secondly, the infestation history of the host does not seem to play an important role regarding the levels of eosinophils at the larval life stage. This is supported by the observation that a higher influx of eosinophils to the attachment site occurs in susceptible breeds in naïve cattle as well as in cattle that have been repeatedly infested (Piper et al., 2010; Franzin et al., 2017).
Lastly, differences are observed amongst larval infestation using different tick species. In the case of Moorhouse and Tatchell (1969) it was found that hours after the attachment of R. microplus larvae to cattle (with previous tick exposure), susceptible cattle presented with a greater number of eosinophils. In contrast, no difference in the influx of eosinophils was observed between resistant and susceptible cattle breeds in response to infestation with the multi-host tick, Haemaphysalis longicornis.
With regards to nymph infestation, Franzin et al. (2017) showed that a reversal of the larval eosinophil response is observed, where upon maturation of tick larvae to nymphs, a greater number of eosinophils occur in resistant breeds (Figure 1.1). The same trend seen during the nymph life stage continues into the adult life stage (Figure 1.1). This has been confirmed in studies using Shorthorn-Zebu vs. Shorthorn (Riek, 1962) and Nelore vs. Holstein-Friesian (Carvalho et al., 2010) cattle infested with adult R. microplus. One study did, however, not confirm this observation. Marufu et al. (2014) identified that the more susceptible Bonsmara (B. t. afrikanus) cattle displayed higher eosinophil levels compared to that of the resistant Nguni (B. t. indicus) cattle breed. To date, it is unknown what the cause of this discrepancy could be.
Chapter 1: Bovine immune factors underlying tick resistance: integration and future directions .
1.4. Skin tissue
1.5. Dynamics of granulocytes and histamine and their suggested involvement in the tickresistance mechanism over the tick lifecycle
1.6. Future directions: potential drivers involved in tick resistance
1.7. Critical evaluation and concluding remarks
1.8. Aims and objectives of the study
1.9. Outputs from this stud
1.10. Additional outputs
Chapter 2: Comparison of the differential regulation of T and B-lymphocyte subsets in the skin and lymph nodes amongst three cattle breeds as potential mediators of immune-resistance to Rhipicephalus microplus
2.1. Abstract .
2.3. Materials and methods
Chapter 3: Temporal analysis of the bovine lymph node transcriptome during cattle tick (Rhipicephalus microplus) infestation
3.3. Materials and methods
3.4. Results .
3.6. Concluding remarks
Chapter 4: In vivo evaluation of Ixodes ricinus induced effects on T and B-cell maturation in the spleen and lymph nodes of BALB/c mice
4.3. Materials and methods
Chapter 5: Concluding discussion
5.1. Problem statement and rationale
5.2. Leukocytes in the skin of tick-infested cattle (Chapter 2) .
5.3. Leukocyte dynamics in the lymph nodes of tick-infested cattle (Chapter 2
5.4. Lymph node transcriptional profiles of tick-infested cattle (Chapter 3)
5.5. The effect of tick attachment and feeding on the transcription profile of draining lymph nodes in Bonsmara cattle (Chapter 3, section 3.5.2.) .
5.6. B- and T-lymphocytes in the draining subiliac lymph nodes and spleens from I. ricinus infested BALB/c mice (Chapter 4