Amino-acid sequence similarity of human and viral encoded chemokines compared to their chemokine receptor targets. Left side of the figure is a comparison of the similiarity of the primary protein sequence of human and virally encoded chemokines (using ClustalW 1.83 and an unbranched dendrogram) with the receptor targets of the specific chemokines seen on the right side of the figure. The names of the virally encoded chemokines are highlighted in bold. On the right hand side a line is used to illustrate that a specific chemokine is a ligand for a specific chemokine receptor. The line is unbroken for endogenous human chemokines and dotted for virally encoded chemokines. The murine lymphotactin has been included to illustrate the great similarity between XCL1 and mXCL1.