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Immunoassay

An immunoassay uses monoclonal antibodies to diagnose infections such as HIV, malaria and chlamydia. This can make disease identification much easier.

Monoclonal antibodies have been made for antigens found on:

• the bacteria Chlamydia trachomatis, which is the cause of the disease chlamydia
• the Human Immunodeficiency Virus (HIV), which is the cause of AIDS
• Plasmodium spp, the protist which is the cause of malaria

Monoclonal antibodies have been attached to dyes that will glow fluorescent under UV light or when radioactive labels are used. When added to infected body fluids, the monoclonal antibodies bind to the antigens and clump together. When observed under UV light or with a radioactive label, it will not only show whether infection is present, but also the extent of infection due to the extent of the fluorescence or radioactive labelling.

Tissue typing

If a person requires an organ transplant, they must wait until a suitable match is found. A suitable match means their tissue type matches the donor organ.

• A tissue type is used to determine the extent to which the immune system of the recipient of a donor organ will react against the donor organ antigens. A poor match could result in the rejection of a donor organ.
• Monoclonal antibodies have been developed which can prevent rejection. They combine with and inactivate helper T cells, without which the lymphocytes that produce antibodies against the transplanted organ won’t work.

Monitoring malaria

An immunoassay can be used to detect the presence of malarial antigens in the blood, such as P. vivax and P. falciparum. Blood samples are taken from many people and their blood is tested with monoclonal antibodies. The labelled antibodies will detect living or dead Plasmodium in the bloodstream. This can show the effectiveness of anti-malarial drugs. For example, if a person’s blood contains the Plasmodium antigen but the person is not suffering the symptoms of malaria, then the drugs work.