Cytotoxic activity against human neuroblastoma and melanoma cells mediated by IgM antibodies derived from peripheral blood of healthy donors

Abstract

A small percentage of healthy donors identified in the Western population carry antibodies in their peripheral blood which convey cytotoxic activity against certain human melanoma and neuroblastoma cell lines. We measured the cytotoxic activity of sera and plasmas from healthy donors on the human neuroblastoma cell line Kelly and various melanoma cell lines. Antibodies of IgM isotype, presumably belonging to the class of naturally occurring antibodies, exerted cytotoxic activity in a complement-dependent fashion. Apart from complement-dependent tumor cell lysis, we observed C3 opsonization in all tumor cell lines upon treatment with cytotoxic plasmas. Cell lines tested primarily expressed membrane complement regulatory proteins (mCRP) CD46, CD55 and CD59 to various extents. Blocking of mCRPs by monoclonal antibodies enhanced cell lysis and opsonization, though some melanoma cells remained resistant to complement attack. Epitopes recognized by cytotoxic antibodies were represented by gangliosides such as GD2 and GD3, as evidenced by cellular sialidase pretreatment and enhanced expression of distinct gangliosides. It remains to be clarified why only a small fraction of healthy persons carry these antitumor cytotoxic antibodies. oligosaccharide-specific monoclonal antibodies or by vaccination with tumor-associated oligosaccharides. For example, treatment with antiganglioside antibodies caused regression of neuroblastoma, 3,4 and clinical trials have been performed using the anti-GD3 monoclonal antibody (mAb) R24 for passive immunization in melanoma patients. 5 In melanoma patients, the level of antiganglioside antibodies was significantly increased after vaccination with a cocktail of gangliosides, and antibody titers correlated with patients' survival. 6 Within the Western population a small proportion of healthy persons carry, within their pool of circulating immunoglobulins, antibodies, preferentially of IgM isotype which can cause a complement-mediated cytolysis of human neuroblastoma cells. 7,8 There are strong indications that these antibodies belong to the class of naturally occurring antibodies (nAb) that are present without external stimulation as products of germ-line encoded genes of the variable region 9,10 and further that a majority of IgM nAb react with carbohydrate antigens. IgM nAb are involved in homeostasis by clearance of damaged or modified intracellular plasma proteins, oxidized lipoproteins or dying cells. 11 Functions attributed to IgM are neutralization, opsonization and complement activation. IgM nAb bind to invading pathogens, which results in complement activation and lysis of the invaders as first line of defense. 11

Diagnostic Profiling of the Human Public IgM Repertoire With Scalable Mimotope Libraries

“…To test the diagnostic potential of the SYM library, we chose to look for reactivity profiles able to separate sera from patients with different brain tumors. Although somewhat questionable, our expectation to find IgM repertoire correlates of brain tumor diseases was justified by (1) reports by Merbl et al (23) that both IgG and IgM natural autoreactive antibody profiling with self-antigens can discriminate between murine tumors and from O'Donnell et al (41) that 3 × 10 5 random peptide-based profiling of antibody repertoires can discriminate GBM from other tumors; (2) reports indicating the role of natural IgM antibodies in the immune surveillance against tumors (7, 30–39, 41–43); and (3) reports of diagnostic or therapeutic natural IgM binding-defined tumor antigens (44–46). Furthermore, cancer is a suitable test for the natural IgM igome's diagnostic utility because of the localized inflammation and shedding of tumor-specific and tumor-associated antigens.…”

The Role of Membrane Bound Complement Regulatory Proteins in Tumor Development and Cancer Immunotherapy

“…It exists in low levels to help the body maintain homeostasis and to recognize cells that have been invaded by a foreign pathogen, and senescent, apoptotic, precancerous, and cancerous cells (19–22). In one such example, the expression of gangliosides GD3 and GD2 expressed on the surface of melanoma and neuroblastoma cells can be recognized by natural IgM antibodies in the sera of a limited number of healthy individuals, resulting in complement mediated cell lysis (23, 24). In another study, an antibody, SC-1, was isolated from a patient with signet ring cell carcinoma of the stomach and found to be reactive to all diffuse-type stomach cancer cells, and around 20% of intestinal-type adenocarcinomas.…”

Effect of membrane‑bound complement regulatory proteins on tumor cell sensitivity to complement‑dependent cytolysis triggered by heterologous expression of the α‑gal xenoantigen

“…The main mCRPs are complement receptor 1 (CD35), CD46, CD55 and CD59 ( 37 , 38 ). CD55 is a membrane glycosyl-phosphatidyl inositol (GPI)-anchored glycoprotein that accelerates the decay of C3 convertases and C5 convertases, leading to the suppression of MAC activation ( 35 ). CD59 is also a small GPI-anchored glycoprotein that prevents the formation of a functional MAC by inhibiting the incorporation of multiple copies of C9 on the target cell membrane ( 37 , 39 ).…”