The Hepatitis A Virus Cellular Receptor (HAVCR1) is a type 1 integral membrane glycoprotein consisting of a six-cell immunoglobulin (Ig)-like domain cysteine ​​extended over the cell surface by a mucin-like domain that contains varying numbers of threonine, serine, and proline. HAVCR1 is a member of the T cell immunoglobulin mucin (TIM) family. HAVCR1/TIM is the only known receptor for HAV infection in human cells. In this study, researchers investigated the interaction of HAV with the HAVCR1/TIM receptor and natural HAVCR1/TIM ligands. The gene encoding HAVCR1/TIM has been shown to be associated with susceptibility to asthma and allergies in humans. HAV infection has shown new results indicating a notable reduction in the risk of developing asthma and allergies as a result of its interaction with HAVCR1/TIM. HAVCR1/TIM is believed to be associated with the regulation of T cell differentiation and the development of atopy. However, the normal functions of HAVCR1/TIM in the absence of HAV infection are not completely understood. The researchers used an expression cloning strategy. They transfected dog cells with a human lymph node cDNA library that confers the ability of the transfected dog cells to produce human immunoglobulins. The binding of transfected canine cells to the HAVCR1/TIM Fc fusion protein is studied. Soluble form of HAVCR1/TIM containing the HAVCR1/TIM Ig variable-type region (IgV) fused to the Fc fragment of the human IgG1 antibody [HAVCR1/TIM(IgV)-Fc]. Materials and methods: Cells and viruses. Perro6D cells derived from canine osteogenic sarcoma D-17 cells transfected with EBNA-1 cDNA are resistant to the G418 antibiotic and have increased transfection efficiency for episomal plasmids containing and the Epstein-virus P1 origin of replication Barr are used to show the possibility... ... half of the article ...... is conducted by researchers to determine whether IgA alone is sufficient to bind to HAVCR1/TIM. They coated the plates with goat anti-human IgG Fc, which will bind to HAVCR1/TIM(IgV)-Fc since the Fc portion in this fusion protein is derived from human IgG. Next, they introduced human IgA into well plates and detected binding of IgA to HAVCR1/TIM(IgV)-Fc. The results showed that IgA itself is capable of binding HAVCR1/TIM without requiring other proteins and cellular components. This confirmed that IgA is indeed a natural ligand of this receptor. Because IgA and HAV are ligands of the same receptor, the researchers reasoned that binding IgA to HAVCR1/TIM would inhibit binding of HAV to the receptor. To address this controversy, they treated GL37 cells with 1, 5, or 10 μg of IgA for 30 minutes and then infected the cells with HAV at a multiplicity of infection (MOI) of 1 to 5 TCID50 per cell.