LLT uses thereof in immune system modulation

Abstract

Natural killer (NK) cells constitute the third major population of lymphocytes. They possess the inherent capacity to kill various tumor and virally infected cells and mediate the rejection of bone marrow grafts. A large family of NK cell receptors belong to the C-type lectin family and are localized to NK gene complex on chromosome 6 or 12 in the mouse or human, respectively. Genes in the NK gene complex are all type II receptors and examples include the families of NKR-P1, Ly-49, and NKG2 receptors. Examples of other C-type lectin-like NK cell receptors that occur as individual genes are CD94, CD69, and AICL. Here we report the molecular characterization of a human lectin-like transcript (LLT1) expressed on NK, T, and B cells and localized to the NK gene complex within 100 kb of CD69. The cDNA encodes a predicted protein of 191 amino acid residues with a transmembrane domain near the N-terminus and an extracellular domain of 131 amino acid residues with homology to the carbohydrate recognition domain of C-type lectins. The predicted protein of LLT1 shows 59 and 56% similarity to AICL and CD69 respectively. We generated a monoclonal antibody (L9.7) against LLT1 and analyzed the functional role of LLT1 in NK cells. Binding of mAb L9.7 induced IFN-g production, but did not modulate cytotoxicity by YT cells, a human NK cell line. We further demonstrate that LLT1 receptor functions as an activating receptor for cytokine production (IFN-g) in resting as well as in IL-2 activated NK cells. Excess amounts of L9.7 mAb failed to increase direct or rADCC cytolytic activity, whereas minimal amounts achieved maximal production of IFN-g by YT and activated NK cells. LLT1 is the first receptor identified that regulate IFN-g production but not cytotoxicity in NK cells.

What is claimed is:  
     
         1 . An isolated antibody that specifically binds to an LLT1 polypeptide.  
     
     
         2 . The antibody of  claim 1 , wherein the antibody is a polyclonal antibody.  
     
     
         3 . The antibody of  claim 1 , wherein the antibody is a monoclonal antibody.  
     
     
         4 . The antibody of  claim 3 , wherein the antibody is L9.7.  
     
     
         5 . A composition comprising the antibody of  claim 3  and a pharmaceutically acceptable carrier.  
     
     
         6 . An assay method for the detection of LLT1 comprising: 
 incubating a sample in the presence of the antibody of  claim 3  to form an antibody-LLT1 complex; and    analyzing the antibody-LLT1 complex formed to detect or quantitate LLT1 in the sample.    
     
     
         7 . A method for activating NK cell production of cytokines comprising: 
 administering to NK cells an effective activating amount of an anti-LLT1 antibody.    
     
     
         8 . The method of  claim 7  wherein the cytokine is IFN-γ.  
     
     
         9 . The method of  claim 8  wherein the antibody is a monoclonal antibody.  
     
     
         10 . A set of amplification primers for amplification of a polynucleotide molecule encoding LLT1, comprising: 
 two or more sequences comprising 9 or more contiguous nucleic acids derived from a polynucleotide encoding LLT1.    
     
     
         11 . A method for analyzing the activity of LLT1, comprising: 
 analyzing cytokine production by NK cells in the presence of an anti-LLT1 monoclonal antibody and in the absence of an anti-LLT1 monoclonal antibody; and    correlating a difference in the cytokine production in NK cells treated by the anti-LLT1 monoclonal antibody versus the NK cells untreated by the anti-LLT1 monoclonal antibody.    
     
     
         12 . The method of  claim 11  wherein the cytokine is IFN-γ.  
     
     
         13 . The method of  claim 11 , wherein the analyzing is in the presence of a test agent, where an increase in cytokine production of the anti-LLT1 monoclonal antibody treated NK cells versus untreated NK cells is correlated with the test agent's stimulation of cytokine production; and 
 wherein a decrease in cytokine production of the anti-LLT1 monoclonal antibody treated NK cells versus untreated cells is correlated with the test agent's inhibition of cytokine production.    
     
     
         14 . A method for treating a host having an infection, the treatment comprising: 
 administering a pharmaceutical composition to the host, the pharmaceutical composition having an effective amount of an anti-LLT1 antibody for causing the production of cytokines by the host.    The method of  claim 14  wherein the anti-LLT1 antibody is L9.7.    
     
     
         16 . A method for modulating the host immune response, the treatment comprising: administering a pharmaceutical composition to the host, the pharmaceutical composition having an effective amount of all or a portion of the LLT1 peptide or DNA.