Cells of myeloid lineage include dendritic cells, monocytes, macrophages, neutrophils, basophils, and eosinophils, while cells of lymphoid lineage include NK cells, B cells and T cells.

Naive B cells (and most other immune cell subtypes) need more than one signal to become activated. They normally need B cell receptor signaling (signal 1), costimulation by other receptors (signal 2), and cytokines/chemokines (signal 3). This system is necessary in order to prevent aberrant activation of lymphocytes (safeguard against autoimmunity).  

In regards to the other statements, there are numerous autoreactive B cells at any given time due to the stochastic nature of VDJ recombination and germinal center reactions. Therefore, tolerance mechanisms and checkpoints are incredibly important to keep these cells in check; central and peripheral tolerance are equally important. Self-nuclear reactive B cells and T cells are both necessary and critical in autoimmune pathogenesis. Female sex hormones are definitely believed to contribute greatly to autoimmune disease pathogenesis (e.g. estrogen). Over 75% of autoimmune patients are women.

Peripheral tolerance is the correct term for the tolerance checkpoint mechanisms that are instituted in the secondary lymphoid organs such as spleen and lymph nodes. B cells with BCR specificities that are low affinity or reactive against self-nuclear antigen will be purged from the repertoire.

The defect in clearance of apoptotic cells in SLE is mainly attributed to macrophages, which serve integral roles in phagocytosis of dead cells and debris. An inability to clear these apoptotic cells over time leads to secondary necrosis, which results in the production and release of several DAMPS or damage-associated molecular pattern molecules which are potent inducers of the immune response.

T cells from the donor must be depleted due to the risk of incompatible MHC antigens on the recipient cells. If there is incompatibility, the donor T cells will attack and kill the host cells resulting in a graft versus host response.

The kidney uses all three of the following processes: filtration, secretion and reabsorption. All three of these processes aid in allowing the body to filter waste products from the blood while retaining nutrients, salts, and water when needed.

Filtration occur when filtrate is separated from blood in the renal corpuscle. Reabsorption is the removal of ions from the filtrate to retain salts. Secretion is the input of salts to the filtrate to eliminate them. All of these processes occur in the nephrons.

The ascending and descending limbs of the Loop of Henle are responsible for creating a countercurrent multiplier system, which concentrates urine and allows water and electrolytes to passively diffuse down their concentration gradients.

All the other options are part of the nephron, but are not responsible for the process of urine concentration. The glomerulus and Bowman's capsule are responsible for collecting and producing initial filtrate from the blood, and form the renal corpuscle. The proximal convoluted tuble is the initial site of reabsorption.

The ascending limb of the loop of Henle is permeable to salt, not water. As salt is removed from the urine, the urine becomes less concentrated. The urine will ultimately be concentrated in the collecting duct prior to excretion. The ascending limb of the loop of Henle helps to establish the salt gradient of the nephron, ensuring that water will be removed from the urine as it travels down the collecting duct, ultimately increasing the final concentration, even by decreasing the immediate concentration.

Antidiuretic hormone (ADH), also known as vasopressin, increases the permeability of the collecting duct to water. This allows a more concentrated urine to be excreted, because water is being lost from the urine to the kidney tissue before excretion. The gradient created by the reabsorption of ions from the loop of Henle means that the interstitium is hypertonic to the collecting duct. If the permeability of the collecting duct to water is increased, we would expect water to flow out of the collecting duct. We would expect ADH levels to increase with dehydration in order to preserve water.

The proximal tubule of the nephron directly follows after Bowman's capsule, and is the first site of reabsorption. Any glucose and proteins that were able to enter the filtrate are removed here via active transport. Most glucose and proteins are blocked from the filtrate by the structure of the glomerulus wall and Bowman's capsule, but those that are able to pass must be removed quickly to maintain the proper oncotic pressures in the nephron. Sodium is perhaps the most important electrolyte in the body; though large quantities of sodium may enter the filtrate, over half of it is reabsorbed in the proximal tubule.

The proximal tubule also serves as a site for reabsorption for potassium and phosphate. Other regions of the nephron closely regulate the reabsorption of bicarbonate and protons, as well as fine-tune the balance of sodium and potassium.