An Ouchterlony double immunodiffusion is performed, crossed lines of precipitation are observed. Which of the following is true?

Which outcome results from improper washing of a tube or well after adding the enzyme-antibody conjugate in an ELISA system?  Assume all steps taken prior to this step were performed properly. 

Mannose-binding protein in the lectin pathway is most similar to which classical pathway component?

Match the appropriate T lymphocyte population with the correct description. 

CD4+ T cells are called helper cells because they help activate other cells; the most important recipients of the CD4+ helper effector function are:

If a slide agglutination test is rotated for less than 1 minute as the directions specify, what source of error can occur?

In an immunoassay, serum is added  to a microtiter well coated with specific antibody. After incubation and washing, enzyme-labeled specific antibody is added. This procedure is:

The most efficient type of antibodies in the agglutination reactions are:

To prepare a 1/5 dilution of serum to saline, how much saline would you use for 0.5 mL of serum?

Substances produced in phagocytes that are toxic to microbes, such as reactive oxygen species, nitric oxide, and lysosomal proteases, do not destroy the phagocyte because they act within: