Immune system

Requires ability to recognize foreign bodies or antigens and mobilize a response.

Must be able the discriminate between self and non-self.

Utilizes memory to rapidly respond to pathogenic antigens that the body has previously encountered.

Men and women differ in their response to foreign and self antigens.

For most infectious disease women have a stronger immune response than do men.

The female immune system response more efficiently to pathogens, producing higher amounts of interferons and antibodies..

Women typically have a stronger innate and adaptive immune responses.

Women have a higher prevalence of autoimmune disease and a greater response to vaccination and a lower severity and prevalence of many infectious conditions.

Must be able to limit responses.

Complex process requiring network of cells and products of such cells that have significant interdependency.

T and B cells are the hallmark of the antigen-specific adaptive immune system.
T-cells orchestrate immune responses both indirectly by providing soluble and membrane associated signals that promote the survival, expansion, and differentiation of B cells which create antibodies that support humoral immunity, and indirectly by killing foreign  and infected tissues through cellular and soluble mediators.
T-cells recognize foreign antigens through a set of T-cell receptors (TCR ‘s) designed to mediate immunity without the collateral damage of destroying native tissues.
Regulatory T cells (Tregs) recognize self peptides and when activated control self reactive pathogenic T cells.
T cells differentiate into a number of subsets with distinct effector cell functions potentially involved in cytokine storm.
Type 1 helper T (Th1) cells inside and cytotoxic T lymphocytes are primarily responsible for the host defense against viral infections.
Th1 cells regulate the recruitment of macrophages, whereas type 2 helper T cells (Th2) recruit eosinophils and basophils, type 9 helper T cells (Th9) recruit mast cells and type 17 T cells (Th17) recruit neutrophils.

Altered in the aging process and becomes less responsive to antigenic challenges, with increases in incidence and morbidity of infections as a result of signaling defects in the aging adaptive immune system.

The innate immune system is activated in the elderly and the occurrence of autoimmune diseases increase as a result.

When the system is impaired inflammation, tissue destruction and autoimmune processes may occur indicating that not all immune responses are protective.

Monocytes, macrophages and the dendritic cells are mononuclear vagus sites and function in innate and acquired immunity.

All mononuclear phagocytes recognize and engulf invading microbes, produce pro-inflammatory cytokines, and process antigens for presentation to naïve T cells, which is secrete various lymphokines.

Cytokines secreted by T cells activate mononuclear phagocytes to destroy enchanted microorganisms.

CD4+CD25+ Foxp3 regulatory T lymphocytes comprise the 5-10% of circulating CD4 positive T cells and migrate to inflammatory sites to control innate and adaptive immunity responses, especially those due to effector lymphocytes of helper T cell subsets: Th1, Th2 Th17, and follicular Th cells.

Treg (T regulatory T cells) cells play a critical role in the prevention of autoimmune disease and also play a central role in the establishment and maintenance of immune tolerance after allogeneic hematopoietic stem cell transplant.


The thymus is the birth place of T cells.
Bone marrow derived CD34 positive stem cells migrate to the thymus, where they differentiate and acquire expression of the TCR-T cell receptor.
Each T cell expresses its own unique receptor, which is composed of a heterodimer of 2 Chains TCR Alpha and TCR beta, each of which is generated through somatic recombination of multiple genetic elements.
This allows for more than 10 to the 10th distinct receptor combinations in provides the ability of the T cell population to recognize the vast array of potential targets.
These capabilities are restricted in their abilities to bind into a self peptide in the context of polymorphic and polygenic component of this ligand, such that molecules are encoded by the major histocompatibility complex: this positive selection ensures the T cells recognize a foreign peptide antigen encoded by self MHC alleles commonly most commonly class I and class II molecules for CD8 positive and CD for positive T cells, respectively.

Innate immune cells, which express invariant receptors that detect microbial products or patterns, include granulocytes, macrophages, and dendritic cells.

Innate immunity is made up of a cellular arm and a humoral arm. 

The molecular strategies used by the cellular arm to sense microbial moieties and tissue damage involve cell-associated pattern-recognition molecules located in different cellular compartments.

These cellular compartments include: plasma membrane, endosomes, and cytoplasm and belong to different molecular families, including toll-like receptors (TLRs), nucleotide-binding oligomerization domain (NOD)–like and retinoic acid–inducible gene I (RIG-I)–like receptors, inflammasomes, stimulator of interferon genes (STING), C-type lectins, and scavenger receptors.

Adaptive immune cells include B cells and T cells, which express highly variable receptors that recognize specific antigens, and mucosal-associated invariant T cells, which express antigen receptors with more limited diversity. 

The mucosal immune system represents the largest component of the immune system, containing approximately 75% of all lymphocytes and producing the majority of immunoglobulin in healthy persons.

The mucosal immunity must simultaneously balance the opposing demands of providing protective immunity against pathogens while preventing excessive immune responses against innocuous food antigens and commensal microbes.


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