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Published on: June 19, 2014
Relevance of ex vivo blood lymphocyte assay for in vivo lymphocyte function
N W Brattig1, C Timmann, R S Abraha
1Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany. NBrattig@bni.uni-hamburg.de
Insights
This study quantitatively links in vitro interleukin-5 (IL-5) secretion by blood cells to in vivo eosinophil activity in humans exposed to parasitic worms. In vitro measurements accurately reflect in vivo immune responses.
Area of Science:
- Clinical immunology
- Parasitology
- Immunological assays
Background:
- In vitro assays of peripheral blood cells are common in clinical immunology research.
- The quantitative relationship between in vitro immune cell activity and in vivo responses has not been well-established.
Purpose of the Study:
- To quantitatively correlate in vitro interleukin-5 (IL-5) secretion by peripheral blood cells with in vivo IL-5 activity, measured by peripheral blood eosinophil counts.
- To assess the utility of in vitro assays in reflecting quantitative in vivo immune cell functions.
Main Methods:
- Studied 458 humans exposed to the nematode Onchocerca volvulus.
- Measured IL-5 in whole-blood cell culture supernatants stimulated with O. volvulus extract or mitogen.
- Correlated in vitro IL-5 secretion with peripheral blood eosinophil counts using multiple regression analysis, including parasite counts.
Main Results:
- A significant quantitative correlation was found between O. volvulus-reactive IL-5 secretion and blood eosinophilia.
- In vitro IL-5 secretion explained 15.1% of the variability in eosinophil counts.
- Accurate correlations were achieved only when parasite counts were included in the multiple regression analysis.
Conclusions:
- In vitro assays using small blood samples can quantitatively reflect the activity of the entire lymphocyte population in vivo.
- This finding supports the use of in vitro immunological assays for predicting in vivo immune status, particularly in the context of parasitic infections.
Abstract:
Determinations of in vitro proliferative and secretory activities of peripheral blood cells are used widely for research in clinical immunology but, to our knowledge, have not been evaluated as to their power to reflect in vivo activities quantitatively. Here, we addressed this question by quantitatively correlating the in vitro secretion of interleukin (IL)-5 by peripheral blood cells to the in vivo activity of IL-5 as reflected by peripheral-blood eosinophil counts. Studying 458 humans exposed to transmission of the nematode Onchocerca volvulus, IL-5 was measured in the supernatants of 0.02-ml whole-blood cells cultured in the presence of O. volvulus extract or mitogen. O. volvulus-reactive IL-5 secretion was correlated significantly to blood eosinophilia in a quantitative manner explaining 15.1% (95% CI 8.3-19.9%) of the variability of eosinophil counts. Interestingly, correlations were obtained only if parasite counts were included in the calculation using multiple regression analysis. The results show that in vitro assays of minute amounts of blood lymphocytes may quantitatively reflect activities of the entire lymphocyte population in vivo.
