The document summarizes the key characteristics and functions of lymphocytes. It describes the three main types of lymphocytes - B lymphocytes, T lymphocytes, and null cells. B lymphocytes mature in bone marrow or bursa of fabricius and produce antibodies, mediating humoral immunity. T lymphocytes mature in the thymus and are responsible for cell-mediated immunity. Null cells have cytotoxic properties and act as intermediates between B and T cells. The document also provides details on T cell subtypes including T helper cells, T suppressor cells, and T cytotoxic cells.

1. Shri Shankaracharya Mahavidyalaya, Junwani , Bhilai
Lymphocyte's
Dr. Sonia Bajaj
(Head of Department)

2. Introduction
• Lymphocyte are mononucleate , nongranular leucocytes of lymphoid tissue,
participating in immunity.
• They are found in blood lymph and lymphoid tissue such as spleen lymph node
tonsil, peyers patches, appendix, etc.
• They are spherical or ovoid in shape. they have a diameter of 7 to 12um.
• They have a large nucleus and a rim of cytoplasm.
• They do not contain endoplasmic reticulum.
• The lymphocyte may be small or large.
• The lymphocyte arise from pluripotential haemopoietic stem cells. some of
the haemopoietic stem cells turn into lymphoid stem cells which in turn
develop into lymphocytes.

3. • The surface membrane or lymphocytes contains
certain unique protein called surface markers.
• The lymphocytes are of three types. They have
B-lymphocytes, T- lymphocyte and null cells.
• The null cells contain about 3% ,the B-cell
about 27 % and the T-cell about 70% of the total
lymphocytes.
• The B-lymphocytes mature in fursa of
fabricius(in aves) or in bone marrow( in
mammal). The B-lymphocyte produce
antibodies and hence they are responsible for
humoral immunity.
• The T- lymphocyte mature in the thymus
under the influence of thymic hormones. The T
lymphocytes bring about cell mediated
immunity.
• The B cells kill bacteria, virus etc. The T-cell are
responsible for the killing of Cancer cells, killing
viral infected cells, allocraft rejection,etc.
• The null cells form a third population of
lymphocytes. They are immediate between T
and B cells. They have cytotoxic property.
Development of Lymphocytes

4. B Lymphocytes
• B lymphocytes that matures in bursa of fabricius or
bone marrow and that brings about humoral
immunity is called B-lymphocyte.The B lymphocyte
are bursa or bone marrow dependent cells.
• The B lymphocyte are Mononucleate , nongranular
leucocytes. They have a large nucleus and a rim of
cytoplasm.
• They found in the blood and lymph. but they are
highly concentrated in the lymph nodes and spleen.
The B lymphocyte contain immunoglobins or their
surface, these are called surface immunoglobulins
(Sig).
• The surface membrane or B cell contain certain
unique protein called B cell surface markes. The B
lymphocytes has a following surface marker –
1. Ia (immune associated) protein which bind with the
Ia receptor of the T-lymphocytes.
2. Fc receptor to bind with the Fc fragment of the
immunoglobulin
3. CRI and CR3 receptor to complement system. surface
immunoglobulins (Sig)of the types IgM and IgD which
act as specific receptor for antigen.

5. T Lymphocyte
• The Lymphocyte are mononuclear , nongranular
leucocytes that mature in thymus and that brings
about cell mediated immunity is called T
lymphocytes.
• The T lymphocytes are thymus dependent cells.
They mature under the influence of thymic
hormones.
• They have a large nucleus and a rim of cytoplasm.
• They are highly concentrated in the blood and
spleen.
• The surface membrane of T lymphocytes
• contain certain unique protein called T cell
surface markers. The T lymphocytes has a
following surface marker-
• 1.Erythrocyte Receptor-It recognises the sheep
erythrocytes(SRBC).
• 2. T cell antigen Receptor (TCR)-It recognizes
MHC major histocompatibility complex class I & II
antigen.
• 3. The Ia protien Receptor- It recognizes the
immune associated protein.

6. T Helper cells
• T helper cells are a sub population of T
lymphocytes that help B cells and other T
cells in immune responses.
• They are the regulator cells.
• They help the B cell and T cell in multiple
ways.
• The T helper cells are represented by TH.
• The T helper cell contain glycoprotein
molecules called CD4 molecules on the
surface.
• T helper cell also called CD4T cells. CD4 is a
immunoglobulin.
• It is a surface receptor.
• The HIV infects mainly the T helper cells.
• T helper cells are nothing but a class of
WBC.

7. T suppressor cell
• T suppressor cells are a sub population of T
cells that suppress the activity of B cells and
other T cells.
• They are the regulatory T cells.
• They inhabit antibody production by B cells.
• They suppress the function of the T killer
cells and T helper cells.
• suppressor T cells are responsible for
immune tolerance by limiting the ability of
the immune system to attack a persons own
body tissues.

8. T cytotoxic cells
T cytotoxic cell (Tc) or T killer cells (TK)
The killar cells are a sub population of T
lymphocytes that kill microorganisms or bodys own
cells.
They are also called the cytotoxic cells.
They are represented by TC or Tk .
The killer cell are effector cells.
They contain on the surface certain molecules called
CD8 molecule. Hence the killer cells are also called
CD8 T cells .
The killer cells kill cancer cells and body cells
infected with virus.

9. B Cells T Cells
Origin
Bone marrow Thymus
Often called
B lymphocytes T lymphocytes
Position
Outside lymph node Inside lymph node
Surface antibodies
Present Absent
Connect
They connect to the surface of invading
bacteria and virus
They connect only to the virus antigen
on the outside
Membrane receptor for antigen
BCR TCR
Life Span
Short Long
Secrete
Antibodies Lymphokines
Types
Only one active type Two types: Helper and Killer
B Cells vs T Cells

10. References-
Immunology –D.Fatima
Immunology – Kuby
Jantu Vigyan- S.M. sexsena
Jantu Vigyan- Dr.H.N. Baijal