Our laboratory has been focused on defining the biologic properties of a cytokine that is now called human recombinant histamine releasing factor (HrHRF). HrHRF activates basophils, eosinophils, and inhibits T cell production of certain cytokines. Recent data suggest there is an additional extracellular molecule that interacts with HrHRF. Furthermore, we have uncovered an explanation for the apparent hyperreleasability of HrHRF-responder (R) donors' basophils. This application will investigate the interaction of HrHRF with an extracellular molecule as well as define the nature of hyper-releasability in HrHRF-R donors' basophils. There are 3 specific aims.
Aim I A. We hypothesize that HrHRF has a unique receptor on the cell surface. IB: We further hypothesize that signaling through the HrHRF receptor involves protein tyrosine phosphorylation. We will identify this receptor and clone it, as well as determine the specific signaling pathways.
In aim 2 A, we will further characterize the HrHRF-R basophil. We have published a negative correlation between the expression SHIP and histamine release to HrHRF. We hypothesize that signal transduction elements downstream of SHIP will demonstrate characteristics distinct from the same pathways in HrHRF-NR donors.
Aim 2 B will investigate the effects of sensitization with IgE from HrHRF-R donors. Finally, Aim 3 will dissect the regulatory mechanisms of SHIP expression and clinical correlates.
In Aim 3 A, we hypothesize that over-expression of SHIP in HrHRF-R donors' basophils will change the phenotype to an HrHRF-NR. We will test this by transducing SHIP into basophils using HIV-TAT protein. We further hypothesize that exposure to a natural allergen and/or cytokine can alter the levels of SHIP protein.
In aim 3 B and 3C, we will follow levels of SHIP protein by culturing basophils in the presence of cytokines and follow donors in and out of a naturally occurring allergy season. In summary, identification of a receptor for HrHRF will be important to identify a blocking molecule that will inhibit the extra-cellular actions of HrHRF on inflammatory cells. Furthermore, it is important to dissect the hyper-releasable phenotype of HrHRF-R donors and establish that SHIP may play a """"""""gatekeeper role"""""""" in human basophils. ? ?
