What Is Candida Albicans and Humoral Response (IgG)

Candida albicans are saprophytic diploid fungus commonly found in the microflora of body cavities. They grow as both yeast and filamentous cells and can cause oral and genital infections especially in compromised immune systems (immunocompromised). Due to their ability to rapidly proliferate, the fungus has become one of the major reasons for hospital-acquired infections (HAI).

Candida albicans is commonly found in the human gut in small numbers. The standard format of existence is in the form of a single ovoid yeast cell. The fungus grows in the same form when cultured in a laboratory medium. In the normal state, it does not cause any problem as the helpful bacteria in the gut can easily control the fungi. In this condition it is unable to penetrate the linings in the digestive tract and no antibodies are produced by the body to suppress the dormant population.

However, Candida albicans may proliferate in certain cases resulting in the prototypic opportunistic disease, Candidiasis. The causes are generally nonimmunogenic such as antibiotics, diabetes and pregnancy, among others or immunologic under which the immune system is unable to stop the proliferation. During this period, the yeast can affect various organs in the body and cause a range of health problems. One of the primary reasons for these infections is the use of antibiotics that damage the physiological and mucosal flora killing both harmful and helpful bacteria, and impair the walls of the digestive tract. Steroids and birth control pills are also responsible for catalysing this growth.

The body's humoral response to the overgrowth is an immune reaction triggered by the macromolecules present in extracellular fluids. The glycoprotein immunoglobulin comprises of five classes, IgA, IgD, IgE, IgG and IgM which act as effector molecules in the humoral response to yeast infections. IgG makes up approximately 75% of the total immunoglobulins in the plasma of normal healthy people while the rest comprise the remaining 25%. The IgA antibody is present in both serum and secretory (sIgA) forms.

The IgG antibodies are generated by the plasma B cells after isotype switching and appear during the maturity of the antibody reaction after repeated contact with antigens. IgG mostly plays a role in secondary immune response due to its delayed appearance and is characterised by relatively high affinity and ability to exist for a longer time. The antibodies bind and coat the pathogens resulting in their immobilisation and takeover by phagocytic immune cells. They also activate the immune protein production in the complement system which helps remove the pathogens. The humoral response to Candida albicans can be studied by enzyme immunoassays. IgA, IgG and IgM assays help detect antibodies against the fungus in human serum.

In healthy human beings, the antibodies are generally able to prevent the yeast infections from affecting other body organs. However, in immunocompromised patients, the fungus can reach the blood and cause Candidaemia. Inadequate and delayed treatment of the disease has been identified as one of the major reasons for increased mortality in hospitalised patients. It is therefore extremely important that proper tests are conducted at the earliest and effective treatment initiated under expert guidance of specialist doctors without any delay.