26388 Cytomegalovirus (CMV) CD8 T-Cell Immune Competence, Quantitative Assessment by Flow Cytometry, Blood (CMVC8)

​​​​CMV (Cytomegalovirus)

Cytomegalic Inclusion Disease (CMID)

Cytomegalovirus (CMV)

CMID (Cytomegalic Inclusion Disease)

​Assessing cytomegalovirus (CMV)-specific immune competence in allo-hematopoietic stem cell transplantation patients who are at risk for developing late CMV disease (beyond day 100 after transplant)  

Assessing CMV-specific immune competence in solid organ transplant patients who are at high risk for CMV reactivation posttransplant

Monitoring immune competence in patients post-primary CMV infection after transplant who are at risk for CMV reactivation after the cessation of antiviral prophylaxis

Identifying individuals who are likely to be protected from posttransplant CMV infection and those who are at higher risk of CMV reactivation

The global CD8 T cell immune competence assay is useful for determining over immunosuppression within the CD8 T cell compartment, when used on transplant recipients and patients with autoimmune disorders receiving therapy with immunosuppressant agents

​Send specimen in original tube.  Do not aliquot.

ORDERING GUIDANCE:

Patient must be cytomegalovirus (CMV)-seropositive and have 1 or more of the 5 major histocompatibility complex (MHC) alleles: HLA A1, A2, B7, B8, or B35 to utilize this assay.

ADDITIONAL TESTING REQUIREMENTS:

It is important to ascertain the patient's and the donor's cytomegalovirus (CMV) serostatus, as well as the patient's MHC class I HLA haplotype, before ordering this assay; see either:

SSO1 / HLA Class I Molecular Phenotype, Blood

DISI / HLA Class I Molecular Typing Disease Association

SHIPPING INSTRUCTIONS:

Specimens are required to be received at Mayo Clinic Laboratories weekdays and by 4 p.m. on Friday. Draw and package specimen as close to shipping time as possible. 

It is recommended that specimens arrive within 24 hours of draw.

Samples arriving on the weekend and observed holidays may be canceled.

NECESSARY INFORMATION:

Ordering physician's name and phone number are required.

SPECIMEN REQUIRED: 

For serial monitoring, we recommend that specimen draws be performed at the same time of day. Timing and consistency in timing of blood collection is critical when serially monitoring patients for lymphocyte subsets. See data under Clinical Information.

The assay is specific for 5 major histocompatibility complex (MHC) class I alleles: HLA A1, A2, B7, B8, and B35, which cover about 70% of the Caucasian population and approximately 40% of the Asian population. It is important to ascertain the patient's and the donor's cytomegalovirus (CMV) serostatus, as well as the patient's MHC class I HLA haplotype, before ordering this assay; see SSO1 / HLA Class I Molecular Phenotype, Blood or DISI / HLA Class I Molecular Typing Disease Association.

Serial assessment of CMV-immune competence posttransplant in the setting of viremia is recommended to establish CMV-specific immune response trends. In the absence of viremia, CMV-immune competence assessment should include a day 100 or later posttransplant specimen or a specimen after the cessation of antiviral prophylaxis in solid organ transplantation patients.

A single measurement of CMV-immune competence is not sufficient to determine immune response to CMV; serial measurements are essential to proper interpretation of the results. Appropriate interpretation of results requires a pretransplant measurement of CMV-specific immunity to assess baseline immune competence.

Since healthy, asymptomatic individuals may not have detectable CMV-specific CD8 T cells, for these individuals, the absence of CMV-specific CD8 T cells alone may not be a risk factor.

The global CD8 T cell immune competence assessment is specific only for CD8 T cells; it does not provide information for overall T cell competence. Further studies are needed to determine if, within the reference range, certain levels of interferon-gamma (IFN-gamma) and CD107a/b expression confer greater or lesser degrees of risk for infectious disease.

​For allogeneic hematopoietic stem cell transplantation (HSCT) and solid organ transplant patients who are cytomegalovirus (CMV)-seropositive and at risk for CMV reactivation, posttransplant results should be compared to pretransplant (preconditioning/baseline) results.

The report includes absolute CD3 and CD8 T-cell counts as well as a derived CMV-specific CD8 T-cell count (derived from CD3 and CD8 T-cell counts). The absolute count of CMV-CD8 T cells that are activated and have cytotoxic function in response to specific CMV peptide is also provided. The data from the 3 components of this assay should be interpreted together and not individually.

In the setting of CMV viremia, frequent monitoring of CMV-immune competence helps define the evolution of the CMV-immune response. In this clinical context, CMV-immune competence should be measured as frequently as viral load to determine correlation between the 2 parameters. CMV-specific CD8 T-cell counts may show a decline in numbers over time in the absence of active infection or antigenemia.

The absence of CMV-specific CD8 T cells may be a risk factor in the immune-compromised or immune-incompetent transplant patient, who is at risk for CMV reactivation. The presence of CMV-specific CD8 T cells may not be protective in itself. If the CMV-specific CD8 T cells do not show appropriate cytotoxic function (due to the fact that they recognize CMV epitopes that do not effectively induce a cytotoxic response), these patients may be at higher risk of an inadequate immune response to CMV infection.

While the reference values provide a guideline of CMV-specific CD8 T-cell numbers and function in a cohort of healthy individuals, baseline (pretransplant/preconditioning) assessments should be taken into consideration when determining CMV-specific immune competence posttransplant. Correlation between data from multiple post-transplant specimens (if available) and the presence or absence of viremia (or active CMV disease) also are useful in the interpretation of results.

CD8 T cell counts are elevated when the immune system is initially reconstituted post-HSCT, and the CD4 to CD8 ratio can be inverted for about 12 months post-HSCT.

Interferon-gamma (IFN-gamma) and CD107a/b expression below the defined reference range are consistent with a global impairment in CD8 T cell function, most likely due to over-immunosuppression. IFN-gamma and CD107a/b levels greater than the defined reference range are unlikely to have any clinical significance.