All nucleated cells have human leukocyte antigens (HLA) on their surface membranes. Although sometimes described as "white cell antigens," HLA characterize virtually all cell types except red blood cells. HLA consist of a glycoprotein chain and a globulin chain. They are classified into five series designated A, B, C, D, and DR (D-related), each series containing 10 to 20 distinct antigens. A, B, C, and D antigens characterize the membranes of virtually all cells except mature red blood cells; DR antigens seem to reside only on B lymphocytes and macrophages (see Chapter 3 - Immunology and Immunologic Testing).

Some antigens have been identified with specific diseases (Table 4-3). Arthritic disorders, for example, have been closely linked to HLA-B27. In addition, HLA typing is valuable in determining parentage. If the HLA phenotypes of a child and one parent are known, it is possible to assess fairly accurately whether a given individual is the other parent.²⁰

• HLA combinations vary according to certain races and populations. The most common B antigens in American whites, for example, are B7, B8, and B12. In American blacks, the most common of the B series are Bw17, Bw35, and a specificity characterized as 1AG. This combination is in contrast to that of African blacks, whose most common B antigens are B7, Bw17, and 1AG. Similar variations among the A antigens also have been found among various races and populations.

• Determination of donor and recipient compatibility for tissue transplantation, especially when they are blood relatives²¹
• Determination of compatibility of donor platelets in individuals who will receive multiple transfusions over a long period of time
• Support for diagnosing HLA-associated diseases (see Table 4-3), especially when signs and symptoms are inconclusive
• Determination of biologic parentage

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).

A venipuncture is performed and the sample collected in a green-topped tube or other blood collection device, depending on laboratory preference. The sample is sent promptly to the laboratory performing the test (not all laboratories are equipped to do so).

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.

• Medicolegal implications: HLA testing results for biologic parentage exclusion are not allowed as evidence in all jurisdictions.