LTC₄, LTD₄, and LTE₄ are cysteinyl leukotrienes (cys-LTs) peptide conjugated lipids derived from arachidonic acid as a result of immune or inflammatory stimuli^1-3.

The above mentioned cys-LTs bind and activate two receptors belonging to the G-protein coupled receptor superfamily, CysLTR1 and CysLTR2 (also named cysLT₁ and cysLT₂ respectively). There is evidence though that other receptors are yet to be identified⁴. These two receptors couple to both pertussis toxin sensitive (G_i/o) and insensitive (G_q, which initiates Ca²⁺ influx) G-proteins for their signaling. The G-protein coupled to is probably determined by which ligand binds the receptor as all three cys-LTs can activate the two receptors albeit with different affinities⁵. In mouse, CysLTR1 and CysLTR2 are subject to alternative splicing. CysLTR1 receptor expresses greater affinity for LTD₄ and binds equally to LTC₄ and LTE₄whereas CysLTR2 has greater and equal affinity towards LTC₄ and LTD₄ over LTE₄⁵.

Human CysLTR1 is highly expressed in spleen, peripheral blood, leukocytes. It is less strongly expressed in lung, small intestine, pancreas and hardly or not expressed in liver, colon, kidney, skeletal muscle, testis heart and brain⁴. On the other hand, CysLTR2 is highly expressed in spleen and leukocytes. Its expression in the heart, brain, spinal cord and adrenal gland differs it from that of CysLTR1⁴.

Cys-LTs and their receptors are involved in respiratory diseases like asthma and other conditions such as cancer cardiovascular, gastrointestinal, skin and immune disorders^1,6.