ImmunologyChapter 3, Lecture 2

• Richard L. Myers, Ph.D.

• Department of Biology

• Southwest Missouri State

• Temple Hall 227

• Telephone: 417-836-5307

• Email: rlm967f@mail.smsu.edu

Lymphocytes

• Lymphocytes are the most important cells of the immune system

• Other white cells play accessory roles– engulfing and destroying microorganisms– presenting antigens– secreting cytokines

Lymphoid cells• Found in blood, lymph, tissue and organs

• Broadly subdivided into B, T and null cells

• Virgin, naïve or unprimed cells are resting

• Antigen causes them to enter the cell cycle

• These cells enlarge into lymphoblasts

• Become either effector or memory cells

• Different groups possess a cluster of differentiation or CD

Lymphocyte

Isolation of mononuclear cells

Lymphoblast proliferation

• Upon antigen interaction, lymphoblasts differentiate into:– effector cells to eliminate antigen

• B cells (plasma cells) and TC and TH cells

– memory cells responsible for life-long immunity

B lymphocyte• Possess sIg, the receptor (BCR) for antigen

• An important B cell marker is CD45 (B220)

• Most B cells express class II MHC

• Antigen presentation causes clonal selection

• Differentiation process produces plasma and memory cells

• Plasma cell secretes a particular class of antibody

Sir F. Macfarlane BurnetBurnet was Director of the Walter and Eliza Hall Institute of Medical

Research, Melbourne 1944-66 and in 1960 was awarded the Nobel Prize

for physiology or medicine with Medawar.

T lymphocyte

• Maturation occurs in the thymus

• T cells possess receptors for antigen (TCR)

• TCR must see antigen associated with an MHC gene product

• Only sees antigen displayed on self cells

• Thy-1 is the earliest marker of a T cell

• Other important markers are CD4 and CD8

T lymphocytes (continued)

• CD4 T cells recognize antigen associated with class II MHC molecules

• CD8 T cells recognize antigen associated with class I MHC molecules

• CD4 T cells function as T helper cells

• CD8 T cells function as T cytotoxic cells

• A suppressor T cell has been proposed

Null cells

• Do not have T or B cell surface molecules

• No antigen binding receptors

• Do not have immunologic memory or specificity

• Some are called natural killer cells (NK)

• Important in tumor immunity

• Some involved in ADCC

Assignment

• Continue reading Chapter 3, Cells and Organs of the Immune System

• Review questions 12 and 13 (pg 83)