“Teach me,” she said.

[Cecily]

Question 4 (Adaptive Defenses)


How do adaptive defenses work? Compare/contrast B cells and T cells. Discuss the different types of T cells. Describe the differences between cell-mediated immunity and antibody mediated immunity.


While our bodies have nonspecific innate defenses which react the same way every time foreign cells are encountered, adaptive immunity is the lymphatic system's approach to conflict escalation. As our former President Bush said once, "There's an old saying in Tennessee, I know it's in Texas, probably in Tennessee that says fool me once, shame on shame on you. You fool me you can't get fooled again."


I wish I had more than an hour left to write this. It's probably my favorite opener for anything I've wrote before.

[Cecily]

I totally glazed over the lymphatic system last time I took A&PII. Really want to get it this time. It's interesting, but complement cascades and cytokines make me check out mentally. Had reservations about an online A&P class, but I'm actually learning so much more in this format. We do the labs in person and all the lecture is online. I get to academic shit post like this every week on the forum:

While our bodies have nonspecific innate defenses which react the same way every time foreign cells are encountered, adaptive immunity is the lymphatic system's approach to conflict escalation. As our former President Bush said once, "There's an old saying in Tennessee, I know it's in Texas, probably in Tennessee that says fool me once, shame on shame on you. You fool me you can't get fooled again." It is quite possible he was talking about adaptive immunity, a process governed by two types of lymphocytes: B cells and T cells. In adaptive immunity, the immune system "recognizes, reacts, and remembers" the foreign substance, "the 3 R's of immunity." The effect of which is a faster and stronger response to threats with subsequent exposures.

B cells originate in red bone marrow. Immature T cells also begin in red bone marrow, then move to the thymus to mature, and then go on to occupy lymphatic tissue. B cells are involved in antibody-mediated immunity and T cells are involved in cell-mediated immunity. Recognition of a foreign antigen stimulates an immune response where these cells multiply and circulate to lymphatic and infected tissue.

Antibody-mediated immunity:
B cells. Secrete antibodies. Provide protection to extracellular antigens (bacteria, viruses, parasites) and toxins.

Cell-mediated immunity:
T cells. Secrete cytokines. Provide protection to intracelluar antigens (bacteria, viruses, fungi) and tumors. Helper and supressor T cells regulate both antibody and cell-mediated immune responses. 4 types.


Helper T-cells: Activate B cells and cytotoxic T cells.
Memory T-cells: Responsible for secondary immune response.
Regulatory T-cells: Immune response control and suppression.
Cytotoxic T-cells: Directly kill foreign cells.

[America]

woopw oop

[Cen]

I want to ask this specifically to you Cecilly, because I think you're likely of the expertise to see right through this. Its more of a riddle:

In world war one, british helmets were upgraded from caps to metal helmets due to a large amount of head wounds from the debris of artillery shells. However, upon issuing the new helmets, the amount of head wounds skyrocketed five fold. The change was almost reverted, but someone realized an error, and the helmets were kept.

Any ideas what the error was?

[America]

British authorities were not counting deaths by head wound as "wounds". Deaths went way down and survived "wounds" went way up.

[Cen]

Since your reply goes to the next page its a perfect reveal of the right answer. Its a question based on a concept of "survivorship bias". Its great to throw at statistics people because it will be almost insultingly easy for them to see, but theres no shame in having great difficulty in it, because survivorship riddles have historically confused some of the greatest minds.

[Cecily]

I had great difficulty understanding the question because it’s the first thing I read when I woke up. Huh, they made helmets out of old shrapnel? Lol. That was illiterally how I was tying to solve it.

I wish it was blatant to me, but I might have missed this one. Thank you for sharing that. It’s a good lesson on why looking at data (and probably things in genral) from a variety different view points is necessary because the obvious conclusion might be the wrong one, no matter how many people believe it.

Gonna look that bias up now.

[Cecily]

^ Looked into that some more. Really good thing to keep in mind, ty.


So, tonight I learned I don't know how to do logarithms anymore.


What is the generation time of a bacterial population that increases from 10,000 to 10,000,000 cells in four hours of growth?



a = number of bacteria at the beginning of a time interval. A = number of bacteria at the end of the time interval


G= T
3.3log a/A


G= T
3.3log 10^7/10^4


G = 240 mins
3.3 x 3


G = 24 mins




Ok. NM. Pretty sure in the past I'd do logarithms by asking lab partner what they got, but it just looks like enter number and press button ??? answer.

[Cecily]

Logarithm quotient rule

The logarithm of the division of x and y is the difference of logarithm of x and logarithm of y.
logb(x / y) = logb(x) - logb(y)


so 10^7 = 10,000,000 = log 7
10^4 = 10,000 = log 4


log 7 - log 4 = log 3


Not sure what the (3.3 x) refers to but just taking their word for it


3.3 x 3 = 9.9


240/9.9 = 24 and change rounded down


I'm starting to figure this out but god dammit logs hurt my head.



Control
500 ml of cottage cheese was inoculated with a 2 ml culture of Pseudomonas aeruginosa and incubated at 25°C. Five hours after inoculation, in a standard plate count there were 200 bacterial cells/ml. After 29 hours at 25°C, there were 1,000,000 cells/ml.


Experiment
500 ml of cottage cheese containing the preservative was inoculated with a 2 ml culture of Pseudomonas aeruginosa. After 6 hours of incubation at 25°C, a standard plate count was performed. There were 700 bacterial cells/ml. After 38 hours, there were 61,000,000
bacterial cells/ml.


Number Log
1 0.00
2 0.30
5 0.70
6 0.78
24 1.38
32 1.51
200 2.30
700 2.85
1.00 × 106 6.00
6.10 × 106 6.79
6.10 × 107 7.79

[Cecily]

1. Why were plate counts used for analyzing bacterial growth instead of direct
microscopic counts or turbidity measurements?

Because it's an experiment over an extended period of time, plate counts would be ideal. The control concentration is too low for turbidity (about 10 - 100 million / mL) and microscopic counts (>10 million / mL), Also, turbidity and microscopic counts have trouble distinguishing live cell counts from dead cell counts. Yet another reason would be the live organism is most likely motile and therefore hard to count with a microscope.



2. How did the control cottage cheese and the experiment cottage cheese differ? What was the independent variable and dependent variable? (Hint: Scientific method)

Independent variable = preservative
Dependent variable = generation time


* I think that's right? It's been a long time since elementary school science.
"The independent variable is the one the experimenter controls. The dependent variable is the variable that changes in response to the independent variable."



3. Determine the effectiveness of the new food preservative by calculating the
generation time of bacterial population in the control versus the experimental
cottage cheese.



Experimental
End: 6.10 x 10^7 = log 7.78
Begin: 700 = log 2.85


G = t/3.3 x log (log 7.78 - log 2.85)
G = t/3.3 x 4.93
G = t/16.269
t = 38 hours x 60 = 2280 mins / 16.27 =
Experimental G = 140 mins

Control
End: 1,000,000 = 1.00 x 10^6 = log 6
Begin: 200 = log 2.30

G = t/3.3 x log (log 6 - log 2.3)
G = t/3.3 x log 3.7
G = t/12.21
t = 29 hours x 60 = 1740/12.21
Control G = 143 mins


Conclusion: The preservative was marginally successful in inhibiting microbial growth.



4. Does this type of test determine bacteriostatic or bactericidal activity?

The goal of a food preservative is to inhibit bacterial growth, not necessarily kill bacteria, so this test would determine bacteriostatic activity.


Pretty sure that's right. Haven't encountered those definitions in any chapter reading yet.




Finally done.