Studies on alpha2-macroglobulin and cytokine interactions

• Main Author: Elliott, Sarah-Francess
• Published: University of Edinburgh 1996
• Subjects: 616.079
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.649995

The aim of the present study was to establish if α<SUB>2</SUB>M bound a number of previously unstudied cytokines of immunological importance, and if so, did this influence their immuno- and bio-reactivity. It was apparent that IL2, TNFα and IFNγ bound to α<SUB>2</SUB>M. For all three cytokines the binding was stronger with α<SUB>2</SUB>M-methylamine (α<SUB>2</SUB>Mm), a chemically altered form of α<SUB>2</SUB>M that has a physiological equivalent. Subsequent biochemical studies were carried out using α<SUB>2</SUB>Mm. To analyse the quantitative interaction of cytokines with α<SUB>2</SUB>Mm, a novel radioimmunoassay system was developed using anti-human α<SUB>2</SUB>M polyclonal reagent as the capture antibody. In addition, the zinc affinity Sephacryl system that had been used in earlier qualitative studies was adapted to a tube system to permit batch analysis of α<SUB>2</SUB>Mm-cytokine interactions. These techniques revealed a binding affinity for IL2 with α<SUB>2</SUB>Mm of k<SUB>d</SUB> = 2.1-2.5 x 10-5M, while that of TNFα with α<SUB>2</SUB>Mm was K<SUB>d</SUB> = 0.97-1.35 x 10-5M. Furthermore, IL2 bound non-specifically whereas TNFα showed a specific interaction with the serum protein. The relevance of such interactions was studied by determining the effect of α<SUB>2</SUB>M on commercial cytokine immunoassays. It was found that α<SUB>2</SUB>M and its derivatives may mask or enhance the detection of a number of cytokines, the effect being dependent on the cytokine and on the source of the kit. The influence of α<SUB>2</SUB>Mm on the bioactivity of IL2 and TNFα was examined in lymphoproliferative and antiproliferative assays respectively. These studies revealed that the complexing of TNFα with α<SUB>2</SUB>Mm ablated its bioactivity, whilst that of IL2 was maintained when complexed with the protein. In conclusion, the results presented corroborate previous work in the literature and extend our knowledge of α<SUB>2</SUB>M-cytokine interactions and its effects.