viral infections

viral infections 

A virus (from the Latin virus meaning toxin or poison) is a sub-microscopic infectious agent that is unable to grow or reproduce outside a host cell.”
Acute virus infection:
Following host entry the virus multiplies and spreads rapidily. and contact with the virus activates host immune responses. Hosts immune mechanisms overcome and eliminate virus. The hosts retains immunological virus and virus survival dependent on rapid dissemination and susceptible hosts aviabliliy.

Characteristics of actute virus disease:
-normally rapid onset.
-symptoms often corresponds with peak viral multiplication.
-often fever and mygalia (from activation of immune response)
-vary in servity from one individual to another.
-Resolve rapidly once the innate immune response develops.

Acute viral infections are serve public health problems.
-usually associated with epidemics
-short incubation period
-delay in indentifibile symptoms until the virus has already spread.
-Acute infections occur in crowded places e.g schools, militariy, nursing homes.

EXAMPLE OF ACUTE VIRAL INFECTION:
RHINOVIRUSES (INFLUENZA)
-common cold often caused by rhinoviruses more than 110 serological types. killed by gastric acid and replicated at 33'C.
-Bind to ICAM-1 on epithelial cell surface and are not easily removed by muco-ciliary secretions.
-enter host cells by translocation
-Lyse host cells after replication and spread to neighbouring cells leading to progressive and extensive damage.
Pathogenesis of the common cold:
-debris from lysed cells provokes a strong inflammatory response
-increased secretion of fluids from lamina propria leads to runny nose and sneezing.
-Phagocytes migrate to to site of infection.
-Release of inflammatory mediators leads to blocked nose and mild fever
-Symptoms are restricted to the upper part of the respiratory tract as these viruses multiply optimal at 33'C and less at 37'C.

Immunity to rhinoviruses
-Rhinoviruses recognises by immune system specific mucosal response -IgA ect rather than humoral response
-immune response quickly clears the infection leading to rapid recovery. (couple of days)
-Immune memory of the infection is retained but is not long lasting as for systematic virus infection.
-frequent reoccurrence of the common cold is due to the larger number >100 of serological distinct strains of rhinoviruses.
EXAMPLE OF ACUTE VIRAL INFECTION: ENTEROVIRUSES.  (MEASLES)

**REMEMBER TO STAY POSITIVE LIKE A PROTON!!**  

positive and negative T cell selection in the thymus.

positive and negative T cell selection in the thymus

 A lymphoid organ is situated in the neck of vertebrates which produces T-lymphocytes for 
the immune system. The human thymus becomes much smaller at the approach of puberty.  

Cortex – immature thymocytes, epithelial cells and scattered macrophages.
Medulla- mature thymocytes, epithelial cells, macrophages and dendritic cells.
T Cell development  in the thymus: 
Step 1: T- cell progenitors develop in the bone marrow and migrate to the thymus-  T cell precursors rearranges its t cells receptor genes in the thymus. 

Step 2: positive and negative selection in the thymus- Immature T cells that recognise self MHC receive signals for survival. Those that interact strongly with self antigen are removed from the repertoire. 

Step 3: Mature T cells migrate to the peripheral lymphoid organs- Mature T cells encounter foreign antigens in the peripheral lymphoid organs are activated. 

Step 4: Activated T cells migrate  to sites of infection- Activated T cells proliferate and eliminate infection. 

T cells move through a number of different developmental stages classified by expression of CD4 and CD8 on their cell surface: They are:
• DN (CD4-8-)
• DP (CD4+8+)
• CD4SP or CD8SP




T cell precursors proliferate extensively in the thymus, but most die there. 95% of thymocytes die by apoptosis before reaching the medulla. Some die due to NEGLECT. 
NEGLECT – no TCR-MHC interaction = NO SURVIVAL SIGNAL
• Positive selection of thymocytes: development of the self MHC-restricted T cell repertoire.  The MHC type of the thymic stroma selects a repertoire of mature T cells that can recognize foreign antigens presented by the same MHC type- self restriction. 
• Only thymocytes whose TCR interact with self-peptide: self-MHC complexes weakly can survive and mature.
• Those that do not recognize the MHC molecules are killed by apoptosis (death by neglect) 
Positive selection is mediated by MHC:peptide on thymic epithelial cells 
Peptides role in positive selection: 
• Peptides presented in the thymus are self –peptides derived from widely expressed 
• Self-peptides presented cause stabilisation of MHC on epithelial cells 
• Self-peptides presented on epithelial cells influence the specificity of the T cells that are selected
• Some self peptides are better than other at positive selection
• Different peptides result in different T cell repertoires
Positive selection coordinates the expression of CD4 or CD8 with the specificity of the T-cell receptor and the potential effector functions of the T cell. This is known as lineage commitment

The Double positive (DP) thymocytes
• DPs initially express low levels of abTCR 
• 10-30% of TCRs recognise cortical epithelial cells expressing ‘self peptide’ presented by ‘self MHC’ – POSITIVE SELECTION
• Positive selection acts on a repertoire of T-cell receptors with inherent specificity for self MHC molecules.
Negative selection removes thymocytes that are capable of strongly binding with "self" MHC peptides. Thymocytes that survive positive selection migrate towards the boundary of the cortex and medulla in the thymus.The remaining cells exit the thymus as immature naïve T cells.

Negative selection of thymocytes: Central Tolerance
• T cells that react strongly (high avidity/strong interaction) with ubiquitous self antigens are deleted in the thymus or become regulatory T cells
• Can occur at the DP or SP stages 
• Can be induced by bone marrow derived antigen-presenting cells in the cortex and medulla such as DCs and macrophages
• thymic medullary epithelial cells can also induce negative selection 

Negative selection is driven by bone marrow derived antigen-presenting cells (DCs and macs) and medullary epithelial cells.

**!!REMEMBER TO STAY POSITIVE LIKE A PROTON!!**

INTERVIEW QUESTIONS

INTERVIEW QUESTIONS 

1.Why do you think it is important for Thames Water to share scientific knowledge among its workforce?

·         Knowledge sharing important because it encourages more connection and collaboration between the workforce.

·         get to know everyone and work in happy environment and be more productive

·         Make everyone knowledgeable about scientific advancements in the field.

·         E.g. from studying the Thames water corporate responsibility and sustainability report suggest that it is important that we share scientific knowledge to help spread awareness of the implications and understanding of how to protect public water supplies and the environment in terms of climate change.

It is important that that employees share their job-related with each other, so that they will be able to perform their job better and eventually lead to higher organization performance. The more knowledgeable individuals are, the more they will be able to innovate. For a company to stay in the game, the employees need to make the most of the knowledge they have- sharing and absorbing it readily.

2.How do you think Thames Water can fulfil its environmental responsibility by sharing scientific knowledge?

·         its written on corporate responsibility and sustainability report. ''responsible and sustainable use of natural resources''.

·         Sending a monthly scientific magazine to all workforce of latest scientific advancements, holding seminars to the public and visiting primary and secondary schools to spread awareness to the general public.

·         creating posters and/or advertising.

Environmentalism is an ideology that evokes the necessity and responsibility of humans to respect, protect and preserve the natural world.* Promoting environmental awareness is a crucial part of being an environmental steward. A way to promote this is by proposing environmentally sustainable and beneficial projects and starting community gardens. As well as constantly educating people. By this way people can understand the economic and biological importance of eliminating the harmful products created by man.

3. What previous experience do you have in teaching or tutoring?

·         very rewarding to tutor people.

·         I have tutored 9 year olds at a elite private school for three years.

·         I am able to explain theories and complex information in a simple and easy to understand and friendly way similarly I way will help my colleagues in understanding.

4. Please give an example when you used your communication skills in teaching or 

tutoring?

·         I helped teach someone how to code and create website as well as buy a website and domain name.

·         I used to be in a computer club.

·         looking for someone with it experience and I know how to use Microsoft office.

Effective communication is the key to human interaction. Whenever I teach, I communicate in a respectful manner. I use a tone that is honest and tactful. When taking on a listening role, I make eye contact and focus on the speaker.

5. How do you see your career progress within the area of teaching?

·         I personally love to teach very rewarding.

·         I like the career prospects and development such as promotional opportunities of career advancement to become of senior instructor &  part of the senior training strategic team.

·         looking to stay with Thames Water for the a long period of time in my life.

·         I can handle responsibility.

Developing my skills as a teacher will not only help you deliver engaging and informative lessons, but it will also help me progress in my teaching career. Continuing professional development (CPD) is a great way of showing employers that I am committed to the company and that I will keep up to date with new approaches of teaching. Personal development way is the best way to learn new skills. And may one day I will have the expertise to have a leadership role.

6. What do you think you will personally bring to the role?

·         I have learned business studies so can help cater to achieve the company goals as well as my scientific understanding.

·         I am determined individual so will try my upmost best to spread the awareness due my duties such as assisting in workshops.

·         I enjoy teaching and open to learn from others.

7. Why are you interested in working  for Thames Water?

·         I like to drink water.

·         I like the career prospects and development such as promotional opportunities of career advancement to become of senior instructor & senior training strategic team.

·          I enjoy the mix of the business and science fields which I have qualifications for both and learned them at A-level.

·         Thames water is the largest water services company in the UK and it will be a privilege to serve the people of the UK providing them with a vital necessity of water.

·        The Thames Water reputation is certainly a key factor, I would be proud to work for a company with such a long history of leadership in the industry.

·        * A friends that works there has told me that the culture supports learning and development and really rewards hard work.

·        * Also my proven track record in teaching and my superb communication skills make me and excellent match for the job requirements.

·        * Also, the role excites me because I love the idea of sharing facts and interacting with people.

**REMEMBER TO STAY POSITIVE LIKE A PROTON!!**