Andrew McLean-Tooke¹, Martyn French²

1. Department of Clinical Immunology, Sir Charles Gairdner Hospital, Perth, WA
2. UWA Medical School and School of Biomedical Sciences, University of Western Australia, Perth, WA

Last Reviewed: September 2019

Introduction

In addition to clinical and virological staging of HIV infection, patients should be staged immunologically as this provides prognostic information for the patient. This is currently undertaken by measuring blood lymphocyte subpopulations using flow cytometry assays, which detect cells expressing surface markers that have been identified by binding of labelled antibodies. For example, T cells express CD3 (part of the T cell receptor for antigens) and can be divided into subpopulations with different functions according to co-expression of CD4 or CD8 molecules with subpopulations of CD4+ and CD8+ T cells identified on the basis of expression of markers of activation or immunological memory. In healthy individuals, the proportions and numbers of these lymphocyte subpopulations remain relatively fixed but may be altered in disease states, such as HIV infection, which is characterised by CD4+ T cell depletion.