Difference Between Monocytes and Lymphocytes

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What are the Differences Between Monocytes and Lymphocytes?

The Human body has special types of cells known as white blood cells which float around the blood and help the immune system fight infections. On average, there are 4500 to 11000 WBC per microliter in the blood. There are five types of white blood cells namely:

  • Monocytes

  • Eosinophils

  • Basophils

  • Lymphocytes

  • Neutrophils

Monocytes

Monocytes are large cells that make 2-8% of the total white blood cell count in the blood. There are three subclasses of monocytes based on the phenotype receptors. Often they are found at the site of chronic infections. They are formed in the bone marrow and released into the peripheral blood.


Structure

Monocytes are ameboid with prominent surface ruffles and measuring between 12-20 μm in diameter. When monocytes enter the tissue it differentiates into a macrophage. The cell shape varies depending on the type of the macrophage(i.e liver, spleen).


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Function

Monocytes have the ability to recognize danger signals through pattern recognition receptors. They are capable of ingesting infectious particles and other large particles but they cannot replace the function of Neutrophils which can remove and destroy infectious particles. Their major functions of monocytes are:

  • Phagocytosis - Cell uses its plasma membrane to engulf large particles.

  • Antigen Presentation - Initiation of adaptive immune responses.

  • Cytokine Production - Fundamental response to injury or infection.

Clinical Significance

An increased number of monocytes occurs when the body is facing chronic infections, blood disorders, stress, diabetes, autoimmune disorders, and certain cancers.

Excess monocytes result in a state called Monocytosis.

The deficiency of monocytes results in leukopenia called Monocytopenia.


Lymphocytes

Lymphocytes originate from the stem cells in the bone marrow and found in blood and lymph tissue. They constitute around 28-48% of the white blood cells. There are two different types of lymphocytes namely; B(Bone-marrow) lymphocytes and T (Thymus) Lymphocytes commonly referred to as B-cells and T-cells. There is another type of lymphocyte called Natural Killer cells which detect and destroy abnormal tissue cells such as cancers. The B-cells make antibodies, which are proteins produced by the body to fight against foreign substances called antigens. They follow the lock and key mechanism wherein they produce one specific antibody to match with a specific antigen. When this happens the antigen is marked for destruction.

The T-cells help in destroying cancerous cells and cells affected by the viruses.


Structure

A normal lymphocyte has a large dark stained, ovoid, or kidney-shaped nucleus with densely packed chromatin. It measures around 6-15μm in diameter.


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Function

The different types of B-cells and T- cells have specific roles to perform, below are a few functions of each:

  1. B-Cells

  • Memory B-Cells - Memory B cells start fast antibody responses when pathogens attack and they remain in the body for a longer duration and remember the previously attacked antigens and help the immune system to respond during future attacks.

  • Regulatory B-Cells - Regulatory B cells have anti-inflammatory effects on the body and prevent lymphocytes that cause inflammation. They also promote the production of regulatory T-cells.

  1. T-Cells

  • Memory T-Cells - They protect against previously found antigens

  • Regulatory T-Cells - They prevent autoimmune diseases, maintain tolerance to germs.

  • Killer T-Cells - They scan and kill the cells that are infected or have turned cancerous.

  • Helper T-Cells - They help other cells in the immune system to start and control the immune response to foreign substances.

Clinical Significance

When there is an increased number of lymphocytes in the blood it results in a condition called Lymphocytes. A high count of lymphocytes in the blood indicates that the body is fighting against infection or inflammation.


A low level of lymphocytes can lead to a condition called Lymphopenia or Lymphocytopenia. Lymphopenia can be acquired along with other diseases or may be inherited.


Difference Between Monocytes and Lymphocytes

Basis of Comparison

Monocytes

Lymphocytes

Percentage count

2-8% of circulating WBC’s.

28-28% of circulating WBC’s.

Lifespan

Monocytes are present in the blood for a span of 24 hours.

On average most Lymphocytes are short-lived they may remain for a few weeks or months but some lymphocytes may remain in the blood for years.

Immunity type

Monocytes are involved in  Innate immunity where the defence mechanisms come into play immediately or within hours of infection or injury when the antigen appears.

Lymphocytes are part of adaptive immunity or acquired immunity which uses specific antigens to mount an immune response.

Size and shape

Large-sized may be spherical or ameboid.

The size varies while encountering an infectious agent.

Cell cytoplasm 

In monocytes, the cytoplasm is opaque, blue-grey in colour with fine lilac granules.

Lymphocytes have clear, transparent, and sky blue coloured cytoplasm without granules.

Vacuoles

Infrequent vacuoles.

Frequent vacuoles.

Foreign body destruction

Monocytes destroy foreign substances by phagocytosis.

Lymphocytes destroy the pathogens by producing antibodies.

Subtypes

Dendritic cells and macrophages are two types of monocytes

T-cells, B-cells, and Natural Killer cells are the 3 types of lymphocytic cells.

FAQ (Frequently Asked Questions)

1. What Does it Mean if the Monocytes and Lymphocytes are High?

Ans: High levels of monocytes in the body mean there is a presence of chronic infection, cancer, or any other auto-immune disorder.

The elevated levels of lymphocytes in the body are called lymphocytic leucocytosis.

2. What is the Main Function of Lymphocytes?

Ans: These are the cells that circulate in the body and are a part of the immune system. The two types of lymphocytes include the T-cells and B-cells. Each type of lymphocyte fights the infection in the body differently. The B-cells in the body are responsible for producing antibodies and the T-cells kill the germs by killing the cells of the body that are affected.