Cytomegalovirus (CMV) infection is a widespread viral lesion of the body, which refers to the so-called opportunistic infections that usually occur latently. Clinical manifestations are observed against the background of physiological immunodeficiency conditions (children in the first 3 to 5 years of life, pregnant women - more often in the 2nd and 3rd trimester), as well as in people with congenital or acquired immunodeficiency (HIV infection, the use of immunosuppressants, oncohematological diseases, radiation, diabetes, etc.).

In response to the introduction of cytomegalovirus (CMV) into the body, an immune restructuring of the body develops. The incubation period ranges from 15 days to 3 months. With this infection, non-sterile immunity occurs (that is, complete elimination of the virus is not observed). Immunity to cytomegalovirus infection (CMV) is unstable and slow. Reinfection with an exogenous virus or reactivation of a latent infection is possible. Due to its long-term persistence in the body, the virus acts on all parts of the patient's immune system. The protective reaction of the body is manifested, first of all, in the form of the formation of specific antibodies of the IgM and IgG classes to CMV. Specific antibodies are responsible for the lysis of the intracellular virus, as well as inhibit its intracellular replication or cell-to-cell spread. Patients' serums after primary infection contain antibodies that react with internal CMV proteins. The serum of recovered people contains mainly antibodies that react with shell glycoproteins.

The definition of IgM is of the greatest diagnostic importance, as an indicator of the activity of the process, which may indicate an acute current disease, reinfection, superinfection or reactivation. The appearance of anti-CMV IgM antibodies in a previously seronegative patient indicates a primary infection. With endogenous reactivation of the infection, IgM antibodies are formed irregularly (usually in fairly low concentrations) or may be absent altogether. The detection of class G immunoglobulins also makes it possible to identify primary cytomegalovirus infection (CMVI), monitor individuals with clinical manifestations of infection over time, and assist in retrospective diagnosis. In severe CMV, as well as in pregnant women and young children, the production of antibodies to CMV is slowed down. This is manifested by the detection of specific antibodies in low concentrations or the absence of positive antibody dynamics.