Lymphocytes

Lymphocytes are cellular components of the blood. They include B cells (B lymphocytes), T cells (T lymphocytes), and natural killer cells (NK cells) and belong to the leukocytes (white blood cells). The size of lymphocytes varies: small lymphocytes: 4-7 μm and medium and large lymphocytes up to 15 μm. The life span ranges from several hours to 120 days. Lymphocytes are determined as part of the differentiation of leukocytes (see “Differential blood count” below).

The procedure

Material needed

  • 4 ml EDTA blood (mix well! ); for children, at least 0.25 ml.

Preparation of the patient

  • Not necessary

Disruptive factors

  • None known

Indications

  • Infections
  • Malignant (malignant) neoplasms

Normal values

Age Absolute values Percentage(of total leukocyte count)
Infants 1,800-10,500/μl 20-70 %
Children 2,000-6,000/μl 25-50 %
Adults* 1,500-3,000/μl 25-45 %

* Relative lymphocytosis: proportion of lymphocytes to total leukocyte count > 45%; without total leukocyte count having to be elevatedAbsolute lymphocytosis: lymphocyte count > 3,000/μl; this is often accompanied by total leukocytosis

Interpretation

Interpretation of elevated values (lymphocytosis).

Interpretation of decreased values (lymphopenia, lymphocytopenia).

  • HIV (chronic infection)
  • Cushing’s disease
  • Hodgkin’s disease
  • Non-Hodgkin’s lymphoma (NHL), single
  • Systemic lupus erythematosus (SLE).
  • Uremia – occurrence of urinary substances in the blood above normal values.
  • Increased risk of death within 9 years (1, 6-fold; +67% for nonhematologic and +179% for hematologic cancers (blood cancers), +88% each for respiratory and cardiovascular diseases (respiratory and cardiovascular diseases), +86% for infectious diseases, and +50% for other causes)
  • Medications:
    • Fumaric acid (dimethyl fumarate)
    • Glucocorticoid therapy/corticosteroid therapy
    • Immunosuppressants (fingolimod)
    • Protease inhibitors (telaprevir)
    • Antiviral (ganciclovir)

Lymphocyte differentiation

Further characterization of lymphocytes is performed by flow cytometric immunophenotyping.

Indications

Differentiation of:

Lymphocyte subpopulation Marker Adults> 17 years Teenagers6-12 year Children2-5 year Children0-2 years
B lymphocytes CD19 abs. 70-830/µl 200-1,600/µl 200-2,100/µl 600-3,100/µl
rel. 7-23 % 8-31 % 14-44 % 4-41 %
T lymphocytes CD3 abs. 600-3,100/µl 700-4,200/µl 900-4,500/µl 1,400-8,000/µl
rel. 60-85 % 52-78 % 43-76 % 39-85 %
T4 lymphocytes (CD4 cells, T helper cells). CD4 abs. 300-2,200/µl 300-2,100/µl 500-2,400/µl 900-5,500/µl
rel. 30-60 % 25-53 % 23-48 % 25-68 %
T8 lymphocytes (CD8 cells, T8 suppressor cells). CD8 abs. 200-1,750/µl 200-1,800/µl 300-1,600/µl 400-2,300/µl
rel. 20-50 % 9-35 % 14-33 % 9-32 %
CD4/CD8 ratio(quotient of T helper to suppressor cells). abs. 0,7- 2,8 0,9- 3,4 0,9- 2,9 0,9- 6,3
Natural killer cells (NK cells). CD56 abs 50-1,050/µl 70-1,200/µl 100-1,000/µl 100-1,400/µl
rel. 5-30 % 4-26 % 4-23 % 3-23 %

Note for practice

  • Persistent lymphocytosis whose cause cannot be plausibly explained must be clarified! This may include bone marrow and lymph node diagnostics.

Immune status – overview of individual parameters

Lymphocytes and their subpopulations.

  • Overall, lymphocytes and their associated subsets represent approximately 30% of all leukocytes stored and circulating in the body. A classification of lymphocytes is made into different subgroups based on their different receptor structures. This form of classification is called CD (cluster of differentiation) classification.
  • T-lymphocytes – T-lymphocytes represent the largest subgroup of lymphocytes, accounting for 70% of all lymphocytes. Characteristic of T lymphocytes is the presence of CD3+ receptors. The development of this group of lymphocytes occurs in the thymus until the precursor cells eventually give rise to antigen-recognizing T lymphocytes. The process of antigen recognition occurs in T lymphocytes through the use of a T cell receptor after antigen is presented by monocytes or macrophages, which develop from monocytes.
  • Ts lymphocytes (T suppressor lymphocytes) – This subset is characterized by the presence of CD3+ and CD8+ receptors. The function of this cell type is the suppression of excessive immune reactions. To perform this function requires interaction of Ts lymphocytes with almost all nucleated cells of the human body.
  • Tc lymphocytes – This subset, which possesses CD3+ and CD8+ as well as CD28+ receptors, represents a population of cytotoxic cells. Analogous to Ts lymphocytes, Tc lymphocytes also require communication with nucleated somatic cells to perform their function. The main task of these lymphocytes is the recognition of virus-infected cells. If the Tc lymphocytes encounter an infected body cell, it is immediately eliminated.
  • Th lymphocytes – In order for the various components of the lymphocyte system to be meaningfully activated, the body requires a cell type to coordinate these defense cells. This task is performed by Th lymphocytes, which have CD3+ and CD4+ receptors. Without the presence of this cell type, it is not possible for the Tc lymphocytes, for example, to destroy virus-infected cells. Via the secretion of interleukins (ILs), there is the possibility of stimulating B lymphocytes, macrophages and cytotoxic T cells.
  • B lymphocytes – In addition to T lymphocytes, there is another important population of lymphocytes, the CD19+ receptor-bearing B lymphocytes. Comparing the numbers of T and B lymphocytes, it is clear that the amount of T lymphocytes is more than 6-fold. In contrast to T lymphocytes, this group of lymphocytes does not require any antigen presentation by macrophages or monocytes, since antigen recognition is performed by membrane-bound immunoglobulins. Furthermore, it is developmentally important to note that B lymphocytes can differentiate into plasma cells. As a crucial task of the B-lymphocytes is the production of antibodies.

Natural killer cells (NK cells).

  • Because NK cells have neither antigen specificity nor a detectable activation mechanism, these cells are considered part of the nonspecific cellular immune system. They are thought to function to destroy tumor cells and virus-infected cells.