NON-MALIGNANT REACTIVE DISORDERS OF LYMPHOCYTES

History

1907 – Turk First describe lymphocytes in a patient whose disease had

been diagnosed as acute leukemia and later recovered. He describe cells as having an immature nucleus and

basophilic cytoplasm similar to that of a plasma cell.1923 – Downey and McKinlay

“Acute Lymphadenosis Compared with Acute Lymphatic Leukemia”.

1967 – Wood and Frenkel Important morphologic and biochemical characteristics of

variant lymphocytes in various clinical entities.

Morphology of Variant or Reactive Lymphocytes

• The most common important feature of variant lymphocyte morphology is the recognition of its benign nature.

• These lymphocytes are normal cells that have been altered as a result of a normal response to stimulus.

• Downey and McKinlay – classic description of the reactive lymphocyte.

Morphology of Variant or Reactive Lymphocytes

• Three distict types:o Type I

Plasmacytoid lymphocyte or Turks’s irritation cells.o Type II

Infectious Mononucleosis (IM)o Type III

Transformed lymphocytes or Reticular lymphocytes

Morphology of Variant or Reactive Lymphocytes

Type I – “Plasmacytoid lymphocyte” or “Turks’s irritation cells”.

• Differentiated cells that are functionally immunocompetent and probably of B-cell origin.• Size: 9 to 20 um diameter• Shape: Oval to Round• Nucleus: Heavy strands or dense blocks of chromation irregularly clumped with sharp, small, defined areas of parachromatin; nuclear shape may be intented or oval. Nucleus membrane is distinct.• Cytoplasm: Basophilia varies but usually the cytoplasm is moderately basophilic. It may be vacuolated, with darker areas of basophilia at the periphery. It may also have a foamy appearance and may contain azurophilic granules.

Morphology of Variant or Reactive Lymphocytes

Type II – “Infectious Mononucleosis (IM)”

• They are predominant in Infectious Mononucleosis.• Size: 15 to 25 um in diameter• Shape: Irregular or Scalloped• Nucleus: The chromatin strands are coarse but not as condensed as those of type I. Rounded masses of chromatin are interspersed throughout. Nuclear shape is round or oval and is rarely lobulated. Nuclear banding frequently is seen in EDTA specimens. Nucleoli usually are not visible.• Cytoplasm: Abundant and often indented by surrounding structures. Nuclear:cytoplasmic ration is 1:2 to 1:4. The cytoplasm has few vacuoles and usually is pale, except for basophilia at the periphery of the cytoplasm and radiating from the nucleus. This cell often has been describe s resembling a friend egg or a flattered skirt.

Morphology of Variant or Reactive Lymphocytes

Type III – “Transformed lymphocytes” or “Reticular lymphocytes”

• Cells in intermediate stage of transformation, the process through which the resting small lymphocyte undergoes blast transformation and ultimately becomes a fully immunocompetent T lymphocyte or plasma cell.• Size: 12 to 35 um in diameter• Shape: Round to irregular• Nucleus Finely reticulated nuclear chromatin (immature). Chromatin strands are finely dispersed with loose, indistinct clumping and poorly defined parachromatin. Nucleoli are usually highly visible and elongated or irregular in shape.• Cytoplasm: Vacuolated with abundant basophilia and a clear perinuclear area.

Lymphocyte Transformation

• The lymphocyte morphology describe reflects the cumulative events following the antigenic stimulation in which the stimulated lymphocyte undergoes structural and biochemical changes, transforming the small lymphocytebto the blastlike-cell, the process is called blastogenesis.

• Transformation can be produced in vitro by a specific and non-specific antigens.

Lymphocyte Transformation• Non-specific antigens used to stimulate lymphocyte in

vitro: Phytohemagglutinin (PHA) Pokeweed Mitogen (PWM) Streptolysin S Staphylococcus Endotoxin (SLS) Antilymphotcyte Globulin (ALG)

• Most commonly used are: PHA and PWM for both T and B cell stimulation leading to mitosis. Cultures in using PHA show nucleolar changes in 4 hours and

RNA production within 8 hours; at the end of 72 hours most cells are transformed and in mitosis.

Lymphocyte Transformation• Transmission Electron Microscope

Nucleus becomes larger and clearer. Cytoplasm contains enlarge Golgi Apparatus. Ribosome increase in number. Mitochondria increase in volume. Endoplasmic Reticulum develops slightly. Azurophilic granules increase in number. Nucleoli become elongated and enlarged.

• Scanning Electron Microscope Reveals a pronounce shape change from round to “hand mirror”

shape. Uropod becomes very prominent.

Differentiation between Reactive and Malignant Lymphocytes

• Both reactive and malignant lymphocytosis may exhibit immature looking cells.

• The major morphologic differentiation lies in the heterogeneity of the variant lymphocytes (polymorphism).

• Malignancies are clonal, and all abnormal cells appear very similar to the other one.

Absolute Lymphocytosis with Variant Lymphocyte Morphology

Absolute Lymphocytosis with Variant Lymphocyte Morphology

• Infectious Mononucleosis A clinical acute contagious viral disease that

affects primarily young adults and teenagers. Self-limited and benign, but serious complications

can occur which occasionally may be fatal. Characterized by variant (reactive) lymphocytes in

the peripheral blood and heterophil antibody-positive serologic test.

Absolute Lymphocytosis with Variant Lymphocyte Morphology• History:

1885 – Filatov – idiopathiclymphadenopathy in children. 1889 – Pfeiffer – lymphatic reaction in children. 1920 – Sprunt and Evans – used the term “Infectious

Mononucleosis”. 1923 – Downey and McKinlay – morphology of the reactive

lymphocytes. 1932 – Paul and Bunnell – Serologic characterization. 1955 – Davidsohn and coworkers – refined serologic

characterization. 1964 – Epstein. Anchong and Barr – herpes-like virus (EBV-

Epstein Barr Virus)

Absolute Lymphocytosis with Variant Lymphocyte Morphology• Clinical Features:

Incubation period of IM is about 11 days. Fever, pharyngitis, and cervical lymphadenopathy are presenting

symptoms in more than 80% of cases. Splenomegaly is found in 50% of cases and hepatomegaly in

approximately 10% of patients. Rash is present in 20% of cases. Complications are pneumonitis, meningoencephalitis, pericarditis,

myocarditis, hepatitis, and laryngeal edema, all of which are related to lymphocytic infiltrates.

Neurologic syndromes such as Bell’s palsy and Guillain-Barre usually are reversible.

Clinical complications include hemorrhage due to thrombocytopenia, airway obstruction due to enlargement of pharyngeal lymphoid tissue, and splenic rupture is splenomegaly is present.

Absolute Lymphocytosis with Variant Lymphocyte Morphology

• Cytomegalovirus Infection• Definition and Clinical Features:

It is a disease caused by cytomegalovirus that closely resembles IM.

Most CMV infections appear to be subclinical. Fever and Splenomegaly are common in middle-aged adults. Hematomegaly may be found in 50% of patients and a rash

may be present. Illness, malaise, fever and chills are common, symptoms may

persist for longer period (3 weeks) Incubation period is 35 to 40 days in adults, and 20 to 25

days for children.

Absolute Lymphocytosis with Variant Lymphocyte Morphology• Pathophysiology:

The virus is found in urine, oral and cervical secretions, and semen, as well as in leukocytes.

Transmission in adults is primarily venereal. More than half of adults possess antibodies to CMV.

Absolute Lymphocytosis with Normal Lymphocyte Morphology

Absolute Lymphocytosis with Normal Lymphocyte Morphology• Acute Infectious Lymphocytosis

• Usually found in children between ages of 1 to 10 years, and occasionally up to 14 years of ages.

• It is contagious, benign, and self-limited.• Causative agent maybe viral or non-viral.• The incubation periods appears to be between 12 to 20 days.• The disease lasts from 3 to 5 weeks and may last as long as 2

months.• Clinical Features:

Asymptomatic – patients with infectious lymphocytosis Symptoms accompany the disease are fever, upper respiratory

infection, diarrhea, and abdominal pain.

Absolute Lymphocytosis with Normal Lymphocyte Morphology

• Bordetella Pertussis Infection Infection in which 79 to 90% of leukocytes on the

peripheral blood film are normal looking lymphocytes.

The increase in small lymphocytes maybe due to redistribution from tissue pools to circulating pools caused by a lymphocyte-promoting factor (LPF).

The leukocytosis and lymphocytosis are pronounced than in any other febrile illness except IM.

Absolute Lymphocytosis with Normal Lymphocyte Morphology

• Lymphocytic Leukemoid Reaction Any condition in which the lymphocytic

leukocytosis is so marked that it gives impression of possible leukemia qualifies as a lymphocytic leukemoid reaction.

Infectious Mononucleosis in children may present with leukocyte counts in excess of 50x109/L, which may lead to an impression of acute lymphocytic leukemia.

Relative Lymphocytosis with Variant Lymphocyte Morphology

Relative Lymphocytosis with Variant Lymphocyte Morphology

• Toxoplasmosis Toxoplasma (Toxoplsma gondii) infection is similar in

clinical presentation to IM, causing fever and enlarged lymph nodes.

The result of the heterophil antibody test is negative. Laboratory features are benign, with normal hematologic

parameters, the exception being a relative increase in lymphocytes and the presence of reactive lymphocytes.

Current test for confirmatory are indirect fluorescent antibody and indirect hemagglutination techniques.

Relative Lymphocytosis with Variant Lymphocyte Morphology

• Miscellaneous Disorders Lymphopenia and neutropenia 10% of patients with thyrotoxicosis have

neutropenia and relative lymphocytosis. The blood probably due to disturbance of adrenocortical function.

Relative Lymphocytosis with Normal Lymphocyte Morphology

• Neutropenia Wide variety of conditions in which the absolute

number of neutrophils decreases, leaving relative lymphocytosis in which lymphocyte morphology is normal.