The mammalian immune system appears to be the most complex of all known animal and plant immune systems. In fact, invertebrates do not possess in general most aspects and the adaptive immune system. Some creatures like fish possess some antibodies but not the full repertoire of antibodies and other factors found in mammalian systems....thus fish appear to possess a "transitional" immune system.
Mammals and humans require the adaptive immune system for survival. And even though invertebrates don't appear to require the adaptive system for survival they do display some immune responses consistent with the adaptive immune response...i.e, rejection of transplanted tissue.
Discuss the evolution and design aspects of the immune systems found in plants, invertebrates, mammals and fish. Do fish really possess a "transitional" immune system? Do any truly "intermediate" adaptive immune systems exist? Do you see design features inherent in the invertebrate immune system which appears to function without an adaptive system?
DUE Sept 28
The immune system in any organism is very complex and requires multiple components to be working properly for its success. Many scientists believe that the innate system is an evolutionary advancement from the adaptive system. They say that the various receptors on the white blood cells are formed from random chance that bind to many different objects. But when one looks at the complete immune system of most mammals and vertebrates, the two types of immune system are woven together. Especially in mammals, the T cells of the less specific innate system activates the more specific adaptive system. The innate system is considered to be older in the evolutionary timeline, but it also seems more complex than the adaptive system which does not fit. There also would be a big jump from the innate system to the adaptive system in the evolutionary process that would create a time in the organisms life to be easily infected with multiple pathogens.
ReplyDeleteAll invertebrates, plants, mammals and fish possess an innate immune system. Primarily as a way of defense mechanisms that can lead to greater mechanisms of destroying an incoming pathogen. Many evolutionists could look at the innate and quickly suggest that it evolved first for it being nonspecific towards pathogens and then evolved into a more specific system (adaptive). But there is much detail in the innate system in the types of responses it includes. There are humoral and cellular responses to an invading pathogen on just the innate level! And these responses can lead to further activation of the adaptive. New studies show that plants, invertebrates, and fish possess Pattern Recognition receptors which can lead to more studies of a more complex innate system in those organisms. There is too big of a jump between the two (as discussed in class) for there to be “evolution” from one to the other. Yes, fish do possess certain characteristics of the adaptive system but because there system does not contain the full repertoire, does not mean that it came from a transition from the innate. Evolutionists may think that because the adaptive is not complex for fish that it evolved from the innate. The systems are intertwined (as Janelle said) but perform different functions and are activated differently.
ReplyDeleteI do not think there is any real evidence of an "intermediate" adaptive immune system existing. I say that because there are such distinct characteristics between the two. The innate is triggered based on a response of certain molecular features. And if a pathogen does not contain certain peptidoglycan pathogens or PAMP's then it can continue on a path to harm the human body. THis is then when the adaptive takes control, not some type of intermediate system. The adaptive is highly specific and can discriminate minor differences in molecular structure. To have an "intermediate" stage would seem like a three part system.
ReplyDeleteOne new study that sticks out is the discovery of PRR's in invertebrates. Having these receptors poses as a design features inherent in the invertebrate immune system that can function without an adaptive system. PRR's can function as Signaling PRRs which include TLR's. When a pathogen breaches an organisms first line of defense, they are recognized by TLRs, which activate immune cell responses. These receptors can play a critical role in invertebrates.
Evolution could claim that invertebrates are the intermediates that eventually evolved into mammals and humans. The fact that they do not necessarily possess an adaptive system like ours, but still have some aspects of an adaptive immunity, leads evolutionist to assume that they are a stepping stone to a more complex organism. However, despite their seemingly logical argument, an argument suggesting a creator provides a better explanation to this enigma. Since invertebrates are not as complex as mammals and humans it would make sense that their immune systems are not as complex as well. Also, invertebrates do not encounter the wide variety of pathogens that larger and more complex mammals do. Therefore, they do not need a highly specific immune system to process, remember, and eliminate a large variety of pathogenic growth.
ReplyDeleteWhile the fish immune system contains two parts, one for physical invasion and one for internal pathogen infiltration, it is by no means as complex as the mammalian adaptive immune system. As a result of this some would classify this as a transitional immune system. However, I would not say that it is transitional because that would suggest that it mutated to a more complex system, that eventually evolved into the mammalian or human system. This would not be logical for the sole reason that mutations are almost always detrimental and are not likely to give rise to more efficient and complex system. I would suggest, however, that this system contains certain aspects of the mammalian immune system. Yet, this system still lacks a mjority of the receptors that the mammalian immune system contains. Therefore, this system could not be considered a translational or intermediate system. The fish immune system is similar to the mammalian adaptive immune system in the aspects that histamines are released when damage occurs and inflammation is a result of that release. With inflammation WBC’s are attracted to that area, just like in our adaptive immune system. In that area foreign bodies are taken away and brought to the kidney or spleen for handling. This is a slight difference in the systems. Another difference is found in the fact that fish do not have memory of pathogens. Therefore, it appears as if this immune system was specifically designed system for fish and not as an intermediate immune system from which the human immune system evolved from.
As for the design features of the invertebrate immune system, it does appear that despite the lack of the adaptive system, they do have a part of their innate immunity that possesses specificity in recognition of non-self. God must have given them the ability to detect the different surface proteins, sugars or carbohydrates on non-self invaders.
Kaylynn, Tori and Janelle,
ReplyDeleteThanks for getting the blog going. Interesting ideas. I think Tori's idea about the fact that different creatures encounter different antigens is interesting. I did not think that idea might hold up at first, but as I think about it ....it has some merit.
I agree with Tori that the immune system of a fish is highly complex for it to be a transitional system. It does consist of two parts, the physical, which helps protect against injury and the environment, and the internal pathogen fighting system. In order for something to be in a transitional or intermediate state, there must be some similarities between the two subjects, but also enough differences at a lower level of complexity that has room to "grow" and evolve into the next stage. A fish's way of fighting off pathogens is highly complex and has many similarities to that of the innate immune system in mammals. They have two components in their blood, antiviral chemical interferon and C-reactive protein that immediately attacks foreign substances. They also show a similarity to mammal's immune system in that they take measures to seal off the entry point of the pathogen through blood clotting and also activate the release of histamine which attracts the WBC's to the area to destroy the bacteria or virus. However some still get through this system, but in these cases, fish still have three ways to fight the disease through the use of antibodies. This shows the complexity of their system. It may not be as complex and intricate as the human immune system, but it is so, it does not support that it is a transitional system. It still has many differences that would not be able to be bridged together through evolution.
ReplyDeleteThey have no recognition or memory of previous pathogens meaning they do not have a type of adaptive system.
What Kaylynn found about the PRR's is very interesting, and again shows the complexity that shows that the system was specifically designed for fish and the pathogens that they will encounter in tier environment.
If the redundancy of the immune system is an advantage as we discussed previously, then it would only make since that if fish didn't need an adaptive immune system, they would still retain some of the redundancies that would serve the innate immune system. However, because of the environment they live in, they don't need quite as complex of a system as we do. As Tori suggested, they don't run into the same pathogens that we do, and maybe they can actually use the physical qualities of water as a part of their immune system.For instance, maybe fish don't need an inflammatory response to infection because they can just swim to hot water to kill the pathogens. The water itself is a protective barrier against any aerobic pathogen. It is possible that God made fish with a full immune system, and then used natural selection through the environment of water to "evolve" a streamlined system. I think a micro evolutionary position could make sense, but there is no way you can leap to the conclusion that they are transitional.
ReplyDeleteThe invertebrate immune system is going to present fundamental differences in many ways. This is to be expected on a design level. As has already been mentioned by my colleagues, the environment that many fish and invertebrates encounter is a far cry from what humans interact with on a day to day basis. While perhaps the waters of the ocean aren't any safer in the way of sustaining pathogenic microbes and antigens, invertebrates combat infections and foreign matter matriculation in many more ways than in humans. Scales and and impermeable exteriors tend to characterize much of the ocean's lifeforms. This immediately sets such creatures apart from humans in a radical way. Our skin is easily punctured and features sweat glands that make for easy microbial harbors. Our respiratory system is continually exposed to air-borne microbes, and the digestive tract is clearly exposed to many various pathogenic substances on a daily basis. We require a much more varied and multi-pronged attack mechanism to defend against the wide variety of pathogenic sources we expose ourselves to. Fish do have internal immune mechanisms designed as a "last resort" to protect against a microbial colony that may somehow find a foot-hold in a fish's body. However, the complex filters in the gills and limited entry points for microbes tends to inhibit microbes. Microbes that utilize water for a living environment are also going to behave differently on a physiological level than most microbes humans will encounter. Emphasis will probably be on motility and speed so as to find food sources more easily in the vast expanse of the ocean. The harsh conditions of the ocean salinity and pH basicity overall, in conjunction with the continually fluctuating temperature makes for a difficult environment for most pathogenic species to thrive and still maintain virulence against invertebrates.
ReplyDeletePlants, invertebrates, fish, and vertebrates all have varying levels of immunity. Evolutionists claim that these different immune systems show a sort of progression, with fish containing the transitional immune system. This would at first glance seem to be an evolutionary progression, but this is not the case. Mammals and humans would not survive without their adaptive immune system. The adaptive immune system is not just a convenient add-on that increases their rate of survival, but is mandatory. Without this system, humans and mammals could not survive. How, then, is it possible for mammals and humans to have evolved from this progression? Another question is what the purpose of evolving this immune system would be. If fish were surviving without the full adaptive immune system, why would they develop it? If evolution takes millions of years for these changes to arise, presumably the organisms would have weeded these useless genes out long before it developed into the mammalian immune system we see today, or if they had a reason for developing this more complicated system, they would have died before evolution could work.
ReplyDeleteAs far as design is concerned, differences in immune systems are expected. Each of these groups of creatures exists in completely different environments in which different pathogens would be encountered, requiring differing levels of immune function. It is only logical to design immune systems specific to each creature, with the exact components needed. Some creatures would require more immune components, while others would require less, depending on their habitats.
Some scientist believe jawed fishes fill the missing link in the series that begins with invertebrates and ends with complex mammalian vertebrates. Jawed fish possess an immune system which contains parts of a traditional adaptive system, like major histocompability complex I & II, Ig, and RAG1/RAG2. None of these things are found in its believed evolutionary predecessor, the jaw-less vertebrate (hag fish, lampreys). The belief is that a need for an "adaptive immune system" or more sophisticated system was needed as fish developed jaws and became more predatory and less parasitic in their behavior, because of the greater exposure to pathogens that prey may carry. As fish continued in their evolutionary process toward mammals, their immune systems also required more complexity because of the increased variety (aquatic, airborne) and complexity of pathogens. So with all this said, it may seem that fish do possess somewhat of an "intermediate" immune system. In contrast of what Tori said in her first paragraph, evolutionist believe that it is because of evolutionary selection, that complex organisms have complex immune systems and simple organisms have simpler immune systems. They believe it was a need based development.
ReplyDeleteBy the way, this is not the stance I support, just wanted to assess the question from the opposite perspective.
Evolutionists are constantly looking for a missing link to fit the puzzles of life together. The human immune system is highly redundant and complex. It contains both innate and adaptive immunity and is highly effective in its function. If humans at one point had to evolve their immune system using something like the “transitional” immune system of the fish, we would not have survived as a species. We were purposefully designed with the immune system we have because it is essential to our proper function. As we saw with our first case study, even something as small as a malfunction in the compliment system can have a huge impact on the ability of the body to fend off infection. At first glance it may seem that there is a logical progression from plant, to fish, to mammalian immune systems. This begins to fall apart when you think about how long evolution is said to have taken. If it took millions of years for the immune system to develop, why do we see so many redundancies in the immune system today? According to evolution, those things that were unnecessary or redundant should have been weeded out and discarded as “bigger and better” systems evolved. This is not something we observe in the human immune system. The immune system is full of redundancies that modern evolutionists have a hard time explaining. The immune systems of plants, fish, and humans are different because we were designed differently for the varying environments we live in and activities we perform.
ReplyDeleteTo me, the idea of a transitional immune system in fish doesn't even make much sense from the point of view of evolution. Evolutionists used to believe that some creatures evolved into toher creatures, but now they believe that the creatures evolved from a common ancestor. So the argument isn't really whether the process of evolution passed through the fish stage to get to the human stage, but why fish would evolve some components of the immune system and why humans would evolve others. I think it's interesting that evolutionists have resorted to the common ancestor approach. They are, in effect, trying to replace a common Designer with a common ancestor. So it seems to me that they need to find a common ancestor, not a missing link in evolution.
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