Anti-Ri antigen antibodies in serum

In a cancer organ, cancer cells express the antigens Ri, Yo , Hu, which can cause the formation of specific autoantibodies. These autoantibodies bind to the corresponding antigens localised in the neural tissue and thus become involved in neurological diseases known as paraneoplastic syndromes.

Paraneoplastic syndromes are defined as clinical syndromes that accompany cancerous tumours without regard to vascular or infectious factors, or arise as a side effect of anti-tumour therapy. Common causes are immunological mechanisms triggered by the tumour, the effects of which can extend away from the location of the primary tumour and/or metastases.  Approximately 15% of cancers, particularly lung and gastric cancers, present with paraneoplastic syndromes.

Paraneoplastic neuro-ophthalmic syndromes usually occur in brainstem encephalitis and/or cerebellar degeneration. The detectable association of paraneoplastic syndromes with various immune responses to onconeuronal proteins or with immunological mechanisms targeting unknown antigens has promoted research into these mechanisms.

A paraneoplastic syndrome or a positive test result for the presence of antibodies to the above antigens may warn of the development of a malignancy even before a cancer diagnosis is made.

Patients who test positive for anti-neuronal antibodies should be immediately checked for the presence of tumours.

The determination of antibodies to Ri, Yo , Hu is essential for the diagnosis and monitoring of the course of the disease and the success of therapy in paraneoplastic neurological syndromes (PNS), as these are associated with cancer. Antitumour therapy is also necessary in the treatment of neurological symptoms .

Antibody testing for the Ri antigen is of diagnostic value in paraneoplastic syndromes (such as opsoclonus-myoclonus syndrome with ataxia, encephalitis rhomboidalis), rapidly growing brain stem tumors, small cell lung cancer, breast carcinoma, and ovarian carcinoma.

Antibody testing for the Hu antigen is diagnostically important in paraneoplastic syndromes and in small cell lung cancer, prostate carcinoma, and neuroblastoma.

However, a small number of patients with paraneoplastic syndrome do not show malignancy in the presence of anti-neuronal antibodies. Some patients with paraneoplastic syndrome may not show anti-neuronal antibodies.