Page 153 - Essential Haematology

Chapter 9 White cells: Lymphocytes / 139

osis includes cytomegalovirus, HIV or toxoplasmo- Immunodefi ciency
sis infection; acute leukaemia; infl uenza; rubella;
A large number of inherited or acquired defects in
bacterial tonsillitis; and infectious hepatitis.
any of the components of the immune system can
cause an impaired immune response with increased
Treatment
susceptibility to infection (Table 9.4 ). A primary
In the great majority of patients only symptomatic lack of T cells (as in AIDS) leads not only to bacte-
treatment is required. Corticosteroids are some- rial infections, but also to viral, protozoal, fungal
times given to those with severe systemic symptoms. and mycobacterial infections. In some cases,

Patients characteristically develop an erythematous however, lack of specific subsets of T cells which
rash if given ampicillin therapy. Most patients control B - cell maturation may lead to a secondary
recover fully 4 – 6 weeks after initial symptoms. lack of B - cell function, as in many cases of common

However, convalescence may be slow and associated variable immunodeficiency, which may develop in
with severe malaise and lethargy. children or adults of either sex. In others, a primary
defect of B cells or of APCs is present.
X - linked agammaglobulinaemia is caused by
Lymphopenia
failure of B - cell development; pyogenic bacterial
Lymphopenia may occur in severe bone marrow infections dominate the clinical course.
failure, with corticosteroid and other immunosup- Immunoglobulin replacement therapy can be given
pressive therapy, in Hodgkin lymphoma and with by monthly courses of intravenous immunoglobu-
widespread irradiation. It also occurs during treat- lin. Rare syndromes include aplasia of the thymus,
ment with the monoclonal antibody alemtuzumab severe combined (T and B) immunodeficiency as a

(anti - CD52) and in a variety of immunodefi ciency result of adenosine deaminase deficiency and selec-

syndromes, the most important of which is HIV tive deficiencies of IgA or IgM. Acquired immune

infection (see p. 390) . deficiency occurs with HIV infection and after

Table 9.4 Classifi cation of immunodefi ciencies.

Primary
B cell (antibody defi ciency) X - linked agammaglobulinaemia, acquired common variable
hypogammaglobulinaemia, selective IgA or IgG subclass defi ciencies
T cell Thymic aplasia (DiGeorge ’ s syndrome), PNP defi ciency
Mixed B and T cell Severe combined immune defi ciency (as a result of ADA defi ciency or
other causes); Bloom ’ s syndrome; ataxia - telangiectasia; Wiskott –
Aldrich syndrome
Secondary
B cell (antibody defi ciency) Myeloma; nephrotic syndrome, protein - losing enteropathy, anti - CD20
(rituximab) therapy
T cell AIDS; Hodgkin lymphoma, non - Hodgkin lymphoma; drugs: steroids,
ciclosporin, azathioprine, fl udarabine, etc.
T and B cell Chronic lymphocytic leukaemia, post - stem cell transplantation,
chemotherapy/radiotherapy, anti - CD52 (alemtuzumab)

ADA, adenosine deaminase; AIDS, acquired immune defi ciency syndrome; Ig, immunoglobulin; PNP, purine
nucleoside phosphorylase.