The Introduction and evaluation of Ki-67 as a read-out method of in vitro lymphocyte proliferation and its application in the investigation of immunodeficiency

Abstract

In the UK, a significant minority of people have a primary or secondary immunodeficiency, leaving them susceptible to severe and/or recurrent bacterial, viral and fungal infections. As part of investigating patients for immunodeficiency, a measure of lymphocyte function is used, namely the proliferation of T lymphocytes in vitro in response to stimulation with mitogens and antigens. Ki-67 is one method for measuring lymphocyte proliferation. Ki-67 is expressed in cells during all phases of the cell cycle but not in quiescent cells, and can be examined by intra-cellular flow cytometric staining alongside other lymphocyte markers.

The aims of this project are:

  • to evaluate and introduce Ki-67 as a measurement of lymphocyte function in a clinical immunology laboratory. • to use this method to examine responses to mitogens and antigens, namely Varicella Zoster Virus (VZV)
  • T cell proliferation to VZV antigen will be examined:

(i) in patients with primary and secondary immune deficiency

(ii) patients with recurrent or severe VZV (iii) before and after Herpes Zoster (HZ) vaccination

Patients with a primary or secondary immune deficiency can have a re-activation of VZV, leading to the development of HZ. The current readout of immunity to VZV is based on measuring patients’ humoral response, in the form of IgG antibodies. There is currently little knowledge on normal cell mediated immune responses to VZV. Measuring lymphocyte proliferation to VZV could be of clinical utility in those that have a known impaired humoral immunity but potentially preserved cellular immunity, to assess the extent of their cellular immunity to VZV. This would allow greater investigation of cellular responses to VZV in patients who have recurrent or severe VZV infection and identify those patients at risk of viral re-activation, who may have normal VZV humoral immunity, as measured by current methods. Once established the method could be extended to other antigens.

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