Download Table 9.1 Functional aspects of T and B cells.

Table 9.1 Functional aspects of T and B cells.
T cells
B cells
Origin
Thymus
Bone marrow
Tissue distribution
Parafollicular areas of cortex in
nodes, periarteriolar in spleen
Germinal centres of lymph nodes, spleen,
gut, respiratory tract; also subcapsular
and medullary cords of lymph nodes
Blood
80% of lymphocytes; CD4 > CD8
20% of lymphocytes
Membrane
receptor
TCR for antigen
BCR (= immunoglobulin) for antigen
Function
CD8+: CMI against intracellular
organisms
CD4+: T-cell help for antibody
production and generation of
CMI
Humoral immunity by generation of
antibodies
Characteristic
surface markers
CD1
CD2
CD3
CD4 or 8
CD5
CD6
CD7
HLA class I
HLA class II when activated
CD19
CD20
CD22
CD9 (pre B cells)
CD10 (precursor B cells)
CD79 a and b
HLA class I and II
Genes rearranged
TCR α, β, γ, δ
IgH, Igκ, Igλ
BCR, B-cell receptor; C, complement; CMI, cell-mediated immunity; HLA, human leucocyte antigen; Ig, immunoglobulin;
TCR, T-cell receptor.
Table 9.2 Some properties of the three main classes of immunoglobulin (Ig).
IgG
IgA
IgM
Molecular weight
140 000
140 000
900 000
Normal serum level (g/L)
6.0–16.0
1.5–4.5
0.5–1.5
Present in
Serum and
extracellular fluid
Serum and other body fluids
(e.g. of bronchi and gut)
Serum only
Complement fixation
Usual
Yes (alternative pathway)
Usual and very efficient
Placental transfer
Yes
No
No
Heavy chain
(γ1–4)
α (α1 or α2)
μ
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Table 9.3 Causes of lymphocytosis.
Infections
Acute: infectious mononucleosis, rubella,
pertussis, mumps, acute infectious
lymphocytosis, infectious hepatitis,
cytomegalovirus, HIV, herpes simplex or
zoster
Chronic: tuberculosis, toxoplasmosis,
brucellosis, syphilis
Chronic lymphoid leukaemias (see Chapter 17)
Acute lymphoblastic leukaemia
Non-Hodgkin lymphoma (some)
Thyrotoxicosis
HIV, human immunodeficiency virus.
Table 9.4 Classification of immunodeficiencies.
Primary
B cell (antibody deficiency)
T cell
Mixed B and T cell
Secondary
B cell (antibody deficiency)
T cell
T and B cell
X-linked agammaglobulinaemia, acquired common variable
hypogammaglobulinaemia, selective IgA or IgG subclass deficiencies
Thymic aplasia (DiGeorge’s syndrome), PNP deficiency
Severe combined immune deficiency (as a result of ADA deficiency or
other causes); Bloom’s syndrome; ataxia-telangiectasia; Wiskott–
Aldrich syndrome
Myeloma; nephrotic syndrome, protein-losing enteropathy, anti-CD20
(rituximab) therapy
AIDS; Hodgkin lymphoma, non-Hodgkin lymphoma; drugs: steroids,
ciclosporin, azathioprine, fludarabine, etc.
Chronic lymphocytic leukaemia, post-stem cell transplantation,
chemotherapy/radiotherapy, anti-CD52 (alemtuzumab)
ADA, adenosine deaminase; AIDS, acquired immune deficiency syndrome; Ig, immunoglobulin; PNP, purine nucleoside
phosphorylase.
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