We have discovered that CD1d-restricted iNKT cells, a lymphocyte subset that normally represents <1% of blood lymphocytes, plays a central role in propagating pulmonary inflammation and injury in the NY1DD sickle cell mouse. Upon activation, these cells release IFN and IL-2 which evoke the production of IFN-inducible chemokines and CXCR3 induction on circulating lymphcytes. iNKT cell activation is inhibited by agonist binding to adenosine A2A receptors. We have shown that selective blockade of iNKT cells with anti-CD1d antibodies, their depletion, or treatment with an adenosine A2AR agonist, significantly reduces substantial baseline pulmonary inflammation and injury in NY1DD mice. Thus, we have established an important new paradigm of sickle cell lung disease by showing that NKT cells that have an invariant T cell receptor (iNKT) are key initiators of lung injury. The central hypothesis of this proposal is that activation of pulmonary iNKT cells in response to lung ischemia plays a critical role in propagating an adenosine-sensitive inflammatory cascade from iNKT to other cells by IFN- and IFN-inducible chemokines, CXCL9 (MIG) and CXCL10 (IP-10) via CXCR3 receptors.
Specific Aim 1 will: assess the consequences of inhibiting iNKT cells or their CXCR3-mediated trafficking on A) baseline pulmonary inflammation and injury;B) accentuated injury (crisis) produced by hypoxia-reoxygenation. Hypothesis: NKT cells play a central role in maintaining an ongoing inflammatory cascade in response to persistent focal lung ischemia. iNKT cells evoke generalized leukocyte trafficking to the lung that ultimately results in secondary lung injury. CD1d blockade or CXCR3 blockade will reduce lung injury in SCD.
Specific Aim 2 will use: A) lymphocyte deficient NY1DD x Rag1 -/- mice;B) NY1DD x A2AR-/- mice;and C) NY1DD x CXCR3 -/- mice, as means of substantiating the roles of iNKT cells, A2A receptors and CXCR3 as mediators of lung injury in SCD. Hypothesis: Lung injury in SCD is due in large part to CXCR3-dependent iNKT cell recruitment and these cells are key targets of A2A agonists.
Specific Aim 3 will assess blood iNKT cell numbers, activation state and CXCR3 expression in the blood of mice and patients with SCD. Patient blood will be shipped from our collaborator, Dr. Joshua Field, who runs the adult SCD clinic at Washington University. Hypothesis: Patients with SCD will have elevated iNKT cell numbers, CXCR3 expression and intracellular IFN that will be correlated to some parameters of disease severity.
Sickle cell disease (SCD) is the most common genetic hematological disorder in the United States, affecting about 80,000 people (1 of every 600 African Americans). It is caused by a point mutation in the sixth codon of the 2-globin gene, and results in replacement of a glutamic acid residue by valine. SCD leads to multi-organ failure, but the lungs are particularly susceptible to injury. We have discovered that a minor lymphocyte subset, invariant NKT cells play an important role in maintaining lung injury in SCD. We propose to investigate how this cells produces lung injury, and the effects of inhibiting its function on lung injury. We also will study iNKT cells in the blood of SCD patients.
