When responding to a specific antigen, mature lymphocytes undergo a series of morphological and biochemical changes that enable them to become actively proliferating cells (immunoblasts). The lymphocytes enlarge, synthesize new nucleic acids and proteins, and undergo a series of mitoses. This proliferative expansion increases the pool of antigen-responsive cells (Fig. 3—4).¹⁵ Immunoblast transformation tests evaluate the capability of lymphocytes to change to proliferative cells and, thus, to respond normally to antigenic challenge.

Several methods of performing immunoblast transformation tests can be used. Nonimmune transformation tests involve exposing a sample of the client's lymphocytes to mitogens, agents that cause normally responsive lymphocytes to become immunoblasts independent of any antigenic effect. Effective mitogens include plant extracts such as phytohemagglutinin (PHA), concanavalin A (conA), and pokeweed mitogen. PHA and conA stimulate primarily T lymphocytes; pokeweed stimulates both T and B lymphocytes, although the effect on B lymphocytes is greater. Approximately 72 hours after the lymphocytes have been incubated with the mitogens, radiolabeled thymidine is added and then incorporated into the deoxyribonucleic acid (DNA) of the proliferating cells. The rate of uptake of radioactive thymidine indicates the extent of lymphocyte proliferation.¹⁶

After immune capability has been established, antigen-specific transformation tests can demonstrate whether the person's T cells have encountered specific antigens; that is, an individual's cellmediated immunities can be documented by observing the way T cells respond to a battery of known antigens (e.g., soluble viral or bacterial antigens or tissue antigens of human white cells from organ donors).

The mixed lymphocyte culture (MLC) technique is widely used in testing before organ transplantation. This test is based on the fact that cultured lymphocytes can recognize and respond to foreign antigens that have not previously sensitized the host. Immunologically responsive lymphocytes cultured together with cells possessing unfamiliar or unknown surface antigens gradually develop sensitivity; after a lag period of 48 to 72 hours, the responding cells undergo immunoblast transformation if the stimulating cells possess antigens different from those of the host.¹⁷

• Radioisotope studies performed within 1 week of the test may alter test results.
• Pregnancy or oral contraceptive use may lead to a decreased response to PHA in nonimmune transformation tests.

• Support for diagnosing immunodeficiency disorders as indicated by a decreased response to nonimmune transformation tests
• Identification of microorganisms to which the individual was previously exposed as indicated by an increased response to antigen-specific transformation tests
• Support for identifying compatible organ donors and recipients as indicated by nonresponsiveness on mixed lymphocyte culture

Nursing Care Before the Procedure

Client preparation is the same as that for any study involving the collection of a peripheral blood sample (see Appendix I).

• All clients should be interviewed to determine whether they have undergone any radioisotope tests within the past week; if the client is a woman, it should be determined whether she is pregnant or using oral contraceptives.

A venipuncture is performed and the sample collected in a green-topped tube or other type of blood collection tube, depending on laboratory preference. The sample should be transported to the laboratory promptly.

Nursing Care After the Procedure

Care and assessment after the procedure are the same as for any study involving the collection of a peripheral blood sample.

• Because the client may be immunosuppressed, assess the site for signs of infection.
• Complications and precautions: Note and report the lymphocyte response to an antigenic challenge in relation to signs and symptoms of tissue rejection or allergic condition.