Abstract: A full-length cDNA encoding a 352-amino-acid protein contains seven regions of hydrophobic amino acids representing membrane-spanning domains of a heptahelix receptor, tentatively named CMKRL1. It shows nearly 30% overall identity with the c5a anaphylatoxin receptors and similar degree of homology with other chemoattractant receptors. Receptor expression was shown in lymphoid cells and tissues. The receptor and antibodies that recognize the receptor are useful for detecting Burkitt's lymphoma and for lowering leukotriene B4 levels in a mammal.