The MACPF domain-containing proteins potentially able to build a transmembrane pore structure are found in the transcriptome of a common periwinkle kidney loaded with trematode rediae. Two homologs of mammalian Macrophage expressed gene 1 (Mpeg1), LlMpeg1-1 and LIMpeg1-2, share similar domain structure with the only difference such as LIMpeg1-2 transcript lacks of a C-terminal transmembrane helix. Expression of membrane-anchored protein LlMpeg1-1 is similar in kidneys of naturally infected with trematode Himasthla elongata and uninfected snails. The expression of the second soluble LIMpeg1-2 protein is 4-fold upregulated under infection. The third MACPF protein found in Littorina littorea kidney is homologous with Perivitellin – 2 67 kDa subunit named LlPV2-67 and the expression of the transcript is 3-fold upregulated in the kidney of infected snails. The last two molecules are candidate effectors that may participate in the immune response of common periwinkles to trematode infestation. A single parasite-expressed MACPF-like protein was recorded from the transcriptome of Himasthla elongata.