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Pneumococcal Opsonophagocytic Assay (OPA) Classic Killing (OPK)

The opsonophagocytic antibody assay measures the level (titer) of opsonic antibody activity in human sera. This assay aids in selecting promising vaccines by demonstrating whether the vaccine-induced antibodies drive efficient complement deposition and subsequent opsonophagocytic killing. This assay utilizes polymorphonuclear leukocytes (PMNs), complement, test antibody, and an antigen target. The antigen target for this assay is live bacteria.

The interaction of antibody with antigen leads to the activation of the complement cascade. The activation of the complement cascade converts C1 to C3b, a protein that serves as an opsonin when bound to an antigens surface. Opsonization mediates phagocytosis, and the antigen (live bacteria) will be consumed and internalized by the phagocyte (PMN). The bacteria colonies are then plated on agar and allowed to incubated overnight. The following day, colonies are counted and percent kill is calculated. The percentage of bacterial kill is used to calculate a titer.

This service provides: instrumentation, scientist/analyst, bulk reagents, disposable supplies, raw data analysis, and biohazard control & disposal. Custom reporting, as well as sample and data archiving is available upon request.

Assay TypeOpsonophagocytic Antibody Assay
Detection MethodManual Counting of Bacteria Colonies
Specimen TypeHuman Serum
Specimen Requirements
  • Separate serum from cells ASAP or within 2 hours of collection
  • Serum must come frozen
  • Minimum Volume - 0.5mL
  • Unacceptable Conditions: Plasma or other body fluids. Contaminated, hemolyzed, or severely lipemic specimens.
NotesFor in vitro research use only, not for diagnostic or therapeutic use.
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