Human Immune Defense Mechanisms Assignment Sample

Exploring Human Immune Defense Mechanisms: Assignment Insights

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Introduction Of Human Immune Defense Mechanisms

The aim of this assignment is to develop an illustrated report based on the Immune system of the human body toward pathogenic organisms. This report will include an explanation, comparison, and evaluation of the various components of the specific and non-specific immune systems that work to protect the human cell from foreign particles. More specifically, this illustrated report will mainly focus on three criteria:

One is an explanation of components of specific and non-specific defence responsible to protect the body, the second criterion is to compare the roles of specific and non-specific defence mechanisms, and the third criterion that will be included in this report is the evaluation of the role of the humoral and cell-mediated response of immune system against foreign particles or pathogens.

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Before initiating this report, it can be stated that the human immune system can be defined as the complex network of organs, cells, and proteins that develop defence mechanisms within the body against any kind of infection whilst protecting the cell and cellular function. This immune system has a vital role- it protects the body from any harmful substances and germ cells. As long as the immune system is running smoothly within the human body, it can provide specific and non-specific defence mechanisms against the pathogen. But if it stops working or become weak to develop a defence against aggressive germ cell, then that concerned individual may get ill.


Explanation of how the various components of specific and non-specific immune systems work to protect the body from pathogen

Specific immune system and its mechanism

Acquired immunity is also known as specific immunity as it tailors the attack to a specific antigen. The specific or acquired immunity is generally developed against the infectious disease mediated by the T lymphocytes and antibodies. According to Smith et al., (2019), phylogenetically specific immunity is being developed or acquired by an individual only after birth- it does not function on its own and is used to cooperate with natural immunity. The basic characteristics of the specific immunity are:

  • Antigen specificity
  • It consists of cellular immune response and humoral immune responses
  • Slower onset than the non-specific immune mechanism

The main cellular components of specific immunity are:

  • T-lymphocytes
  • B-lymphocytes
  • Plasmatic cells – these are originated in the bone marrow and developed from the lymphoid progenitor.

The T-lymphocytes or also known as the T-cells are developed in the bone marrow and move to the thymus through the bloodstream, where it gets matured. The three main mechanisms of T-lymphocytes are to act as chemical messengers to activate the immune responsive cells to develop the specific or adaptive immune response with T-helper cells. Additionally, T-lymphocytes are used to work as to detect the cells which are infected by viruses or tumour cells, and ad that time cytotoxic T-cells destroy the foreign particles. Some of the T-helper cells turn into memory T cells (Smith et al., 2019). On the other hand, B-lymphocytes are also made and mature in bone marrow. B cell in specific immune responsive mechanism, used to activated by the T helper cells. T-helper cells are used to activate the B-cells in the presence of antigens. The antigen-specific T-cell response activates the B cells and triggers them to transform into plasma cells. The plasma cell can quickly produce antigen-specific antibodies and release those into the bloodstream. Some of the activated B cells can transform into memory cells and become the “memory” of the specific or adaptive immune response (van der Willik et al., 2019).

Humoral components of the specific immune responses used consist of antibodies and cytokines.

Antibodies are made up of protein and sugar that are used to circulate in the bloodstream. In the phagocytosis and opsonization process, antibody plays the most important role by incorporating with the natural immune cells. The three main functions of antibodies are neutralizing the germ cells by directly attaching to the targeted antigen at the cell surface. Antibodies are used to activate the immune system by attaching to the cell surface- scavenger cells are better to develop aggressive immune responses against pathogens, which are loaded with antigen-specific antibodies (Roy et al., 2022). Another important function of antibodies is to activate the proteins which in turn can help the cell to develop an immune response.

Non-specific immune system and its component and mechanism

Majority of the viral infections are limited by the non-specific defence, which

  • Restrict the viral multiplication to a manageable level
  • To initiate recovery from established infections that is completed by the combination of the early nonspecific and subsequent antigen-specific immune defence (Harms et al., 2021)
  • To make the host enable for cope with the peak number of viruses

Non-specific immunity is also known as the innate immune response or innate immunity, which is comprised of secretory molecules, cellular components, and anatomical barriers. The anatomical barriers are made up of skin and the internal epithelial layers associated with the protective surface and biological agents (Pelissier Vatter et al., 2021). The humoral innate immune response consists of multiple components including Nabs or naturally occurring antibodies, pentraxins, and the contact and complete cascades.

Naturally occurring antibodies are produced by B1 B lymphocytes. Nab are particularly germline-encoded antibodies that comprise restricted epitope specificities and are produced in absence of the external antigen stimulation. IgM can be considered as naturally occurring antibodies but it can also include the Ig A and IgG isotypes (Warwick et al., 2021). The function of naturally occurring antibodies is to mediate the clearance of cellular debris, and apoptotic cells by opsonization. Additionally, in the case of the innate immune response, the naturally occurring antibodies can recognize a wide range of pathogens, and initiate the adaptive immune responses by interacting with the dendritic cell, B, and T lymphocytes.

Pentraxins is the multimeric pattern recognition protein or can be termed as the acute phase protein which can be synthesized and act as the marker of infection, tissue damage, or any kind of inflammation in the cell. The pentraxins are used to contain the common domain of the C-terminus. The short pentraxins contain the CRP or c-reactive protein and SAP or serum amyloid P protein which are produced in the liver (Warwick et al., 2021). The Pentraxins are multifunctional and act as a nonredundant component in innate or non-specific immune responses. It plays one of the important roles in human disease by interacting with multiple components that take part in humoral responses (Rispens and Huijbers, 2023).

Apart from that, Squamous cells, columnar cells, Phagocytic cells, NK cells, Interferons, TNF-alpha, complement, and fibronectin are some important components associated with the innate or non-specific immune response.

Complement or complement activation is used to take place in three pathways- classical, alternative, and MBL or mannose-binding lectin pathway. Every pathway comprises the C3 convertase which separates the C3-producing protein C3n and C5 convertase. The action of C3 and C5 convertase produces the anaphylatoxins, C5 and C3a which play important roles in the humoral innate or non-specific immune response (Smith et al., 2019). The main function of complement is to maintain the homeostasis requires to regulate the cascade reaction.

Compare the specific and non-specific defence mechanisms in terms of specificity and speed of their response to infection

Specific defence or also known as adaptive immunity is comprised of two main functions- recognition and coordination of the attack against specific pathogens. Specificity refers to the ability of the adaptive response or immune system to target the specific pathogen and memory indicated the ability to respond to that pathogen which is already been exposed to the immune response. According to Du and Yuan, (2020), specificity can be defined as the degree to which the immune response or defence mechanism of human immune cells can discriminate between different antigenic variants. It is therefore an approach to measure the relative binding affinity of antibodies or T cell receptor protein to antibody-specific antigens. This discrimination depends on several pathogen variant bonds, on the antibody binding affinity, and on the stringency of the scenario in which the assay used to be conducted. In the case of the adaptive immune response or defence mechanism, the specific subset of the antigen molecule is used to recognize by the T cell receptors, which can be defined as the epitope. Epitopes primarily have made up of 15 amino acids by the spatial contact of the antibody and the epitope during binding. In response to the specificity, in the case of a specific immune response or defence mechanism, the foreign substances used to be phagocytosed by the macrophage and white blood cells (lymphocytes) and by antigen-presenting cells (Morandi et al., 2020). The host cell contains antigen-binding receptors which are known as histocompatibility complexes or MHC types 1 and 2. MHC 1 is crosslinked with the CD8 lymphocytes while MHC 2 is crosslinked with the CD4 lymphocytes. T cells and B cells are the major component in specific defence mechanisms and comprise multiple antigen receptors. At this time, CD4 T lymphocyte gets activated by the receptor cross-linkage and produce cytokines which in turn can promote the proliferation of selected lymphocytes (Roy et al., 2022). This formation of new lymphocytes with specific receptors can cause the activation of B cells which form the antibodies. This mechanism triggers the destruction or phagocytosis of the foreign particles.

On the other hand, CD8 T lymphocytes get activated by another receptor cross-linkage activity and produce substances that are toxic t the pathogens. Therefore, in terms of specificity and speed, a specific defence mechanism works on two occasions- when the foreign particles enter the body for the first time, the defence mechanism is used to start in dilemma till the aforementioned process starts to the extent that the effect is visible. This phenomenon is known as primary response, at that time, IgM or immunoglobulin is formed and the primary response has a smaller magnitude than the secondary response (von Roemeling et al., 2020). After the initiation of the primary response, some T lymphocyte and B lymphocyte cells are used to get matured into the memory cell and act as the shortcut when the foreign antigen enters the body for the second time. Therefore, this response is known as a secondary defence mechanism which is large and quick in action.

Therefore, it can be stated that in terms of specificity, adaptive defence mechanisms contain large repertories of antibodies, T cell antigen receptors, and variable lymphocyte receptors. In combination, these receptors act as the recognition repertoire which can increase the chance that adaptive immune response and responsible cell receptors can detect the possible and probable antigen encountered in the cell. TCR and BCR or T cell antigen receptor and B-cell receptors, are the core component in specific defence mechanisms used to generate by somatic cells by site-specific DNA recombination and every receptor has a particular specificity. According to Cassaniti et al., (2022), TCRs are used to scan the composite surface produced by the MHC molecule and the peptide residing in its groove and relay this information to the interior of T cells. A single TCR antigen-binding site can showcase high specificity.

On the other hand, a non-specific defence mechanism results from the integration of multiple positive and negative signalling. The "missing self" model of NK cell activation is the process of integration of positive and negative signalling. In comparison to the adaptive response, in the case of the innate defence, the recognition is comprised of Priori or no "specific" ligand for the TCR. A given peptide-MHC or p-MHC ligand acts as the cognate after the successful activation of the specific T cell clone (Côté-Gravel et al., 2019). In the case of vertebrates, the innate and adaptive defence mechanisms can be distinguished based on the level of specificity. In the case of adaptive immunity, the defence mechanism is highly specific whereas in the case of innate immunity, the defence mechanism for the immune response is less specific, when it comes to recognising the pathogens by the innate immune receptors. In the case of innate immunity, the antibody receptors used to recognize the limited number of molecules-some of those are evolutionarily conserved and shared by infectious agents like peptidoglycan, non-methylated CpG, lipopolysaccharides, double-stranded RNA in non-specific defence mechanism, the recognition sensor is known as pattern recognition receptors which include Toll-like receptors or TLR (Iqbal, 2020).

Innate receptor ligands in non-specific defence used to be self-originated and polymorphic and those are exemplified by the Natural killer cells or NK receptor-ligand pairs and KIR. The specificity of innate immune response and defence mechanism can also be recognized by analysing the innate sensors. Another difference between the Non-specific defence and specific defence mechanism is tahr in the case of the innate immune response, the recognition of antigen is substance-specific (Du and Yuan, 2020). For example, chemical substances are used to work for destroying the pathogens which are already phagocytosed. These include enzymes, cytokines. Cytokines are a series of protein substances which are secreted by the cells and responsible for engulfment of the foreign particles. In this defence mechanism, the phagocyte recognises and binds with the pathogen and uses the plasma membrane to engulf that pathogen inside the cell, whereas in the case of a specific defence mechanism, T and B cell receptor proteins are responsible to show immune response, for which the specific defence is more specific and fast than the non-specific defence mechanism (Rispens and Huijbers, 2023).

Evaluation of relevance, significance and advantages and disadvantages, strength and weakness of the humoral and cell-mediated immune response

The humoral cell response and cell-mediated immune response are two forms of the adaptive immune system which can allow the human body to remain protected from foreign particles or pathogens. The humoral or antibody immune response is considered to be essential for the host cell to develop a defence against bacterial or any foreign pathogens. The lungs, for example, have the ability to respond to some pathogens by stimulating the residential antigen-specific memory B cells. On the other hand, after exposure to the new pathogen, the lung generates "de novo" systematic and local antibody responses which result in the production of antigen-specific IgG and IgA which help to clear out the invaded pathogen and reduce the colonization of respiratory epithelial cell (Warwick et al ., 2021). In such an immune response, the activation of the B ce;l and antibody-secreting plasma cells is triggered by the antigen and it then requires the helper T cells. The helper T cells comprise the TH2 and CD4 T cells and the subset of the TH1 cell which can help the B-cell activation.

Humoral adaptive immunity can be defined as the adaptive immune response where B lymphocyte and plasma cell or effector B cells are used to produce antibodies against the foreign particles. It in turn stimulates the T lymphocyte cell to attack the pathogen and this immune response is used to mediated by the antibodies. The advantage of the humoral immune response is that the mechanism is used to work based on substances that are found in body fluids or humour. Therefore, this specific immune response is known as antibody-specific/ mediated immunity (Harms et al., 2021). Another advantage or significance of the humoral immune response is the defence mechanism is specific and generated against each particular antigen. This immune response is essential for the host's defence mechanism against pathogens like pneumococci. The major drawback or disadvantage of passive humoral immune response is that the antibodies do not stay within the bloodstream for a very long period, because the human body continuously reacts with the specific pathogens and the antibodies used decay or are destroyed without restocking.

Unlike the humoral immune response, cell-mediated immunity does not depend on antibodies to develop adaptive immune function. Cell-mediated immunity is primarily driven by the mature T cells macrophages and by the cytokines. T cells which take part in the cell-mediated immune response, contain membrane-bound MHC class 1 protein which is used to recognize the intracellular antigen (Roy et al., 2022). The binding specificity between the foreign particles and MHC proteins is significant for maturation and differentiating the naïve T cell from the helper T cells. The advantage and relevance of cell-mediated immune response is it works on the specific region of the body, where the cell is infected by any virus or fungi, which can be termed intracellular invaders. The advantages of this immune response are:

  • Other than humoral immune response, in the case of cell-mediated immunity, the activating antigen-specific cytotoxic T-lymphocytes or CTLs can destroy the cell with epitopes of the pathogens on their surface (Morandi et al., 2020).
  • The activated macrophages and NK cells enable to destroy of the intracellular pathogen
  • In this immune response, the stimulating cells secrete different cytokines that in turn can influence the function f other cells, which are involved in adaptive immunity and innate responses.

Additionally, in terms of the relevance and significance of this specific immune response, cell-mediated immune response does not involve the antibodies and provides direct action to the microbes that survive in phagocytosis. This immune response is effective to destroy virus-infected cells, intracellular bacteria and cancer. The major negative impact of cell-mediated immune response is during the viral infection. During the viral infection, this specific immune response is not always beneficial and can cause damage to the host cell which manifests the immunopathology.


In this report, an in-depth analysis of the human immune response and defence mechanism has been carried out. This report includes the identification, comparison and evaluation of the human immune responses and the activity or components related to the immune response reaction. Immunity is an important factor to make the human body protected from pathogens. There are different substances and cells which are responsible to develop this defence mechanism within human cells.


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